Refactor ProcessDetails and PreemptivePriorityScheduling (#5448)

* Refactor ProcessDetails and PreemptivePriorityScheduling for consistency

* fix formatting

* fix formatting

* Improve test readability and maintainability

.devcontainer/Dockerfile

@@ -1,8 +1,8 @@
 # See here for image contents: https://github.com/microsoft/vscode-dev-containers/tree/v0.238.0/containers/java/.devcontainer/base.Dockerfile
 
 # [Choice] Java version (use -bullseye variants on local arm64/Apple Silicon): 11, 17, 11-bullseye, 17-bullseye, 11-buster, 17-buster
-ARG VARIANT="17-bullseye"
-FROM mcr.microsoft.com/vscode/devcontainers/java:0-${VARIANT}
+ARG VARIANT="21-bullseye"
+FROM mcr.microsoft.com/vscode/devcontainers/java:1.1.0-${VARIANT}
 
 # [Option] Install Maven
 ARG INSTALL_MAVEN="false"

.devcontainer/devcontainer.json

@@ -8,7 +8,7 @@
 			// Update the VARIANT arg to pick a Java version: 11, 17
 			// Append -bullseye or -buster to pin to an OS version.
 			// Use the -bullseye variants on local arm64/Apple Silicon.
-			"VARIANT": "17-bullseye",
+			"VARIANT": "21-bullseye",
 			// Options
 			"INSTALL_MAVEN": "true",
 			"INSTALL_GRADLE": "true",

.github/CODEOWNERS

@@ -1 +1 @@
-* @yanglbme @vil02 @BamaCharanChhandogi
+* @yanglbme @vil02 @BamaCharanChhandogi @alxkm @siriak

.github/dependabot.yml

@@ -10,4 +10,9 @@ updates:
     directory: "/.github/workflows/"
     schedule:
       interval: "daily"
+
+  - package-ecosystem: "maven"
+    directory: "/"
+    schedule:
+      interval: "daily"
 ...

.github/workflows/build.yml

@@ -6,10 +6,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - name: Set up JDK 17
+      - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: 17
+          java-version: 21
           distribution: 'adopt'
       - name: Build with Maven
         run: mvn --batch-mode --update-snapshots verify
@@ -29,3 +29,9 @@ jobs:
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
           fail_ci_if_error: true
+      - name: Checkstyle
+        run: mvn checkstyle:check
+      - name: SpotBugs
+        run: mvn spotbugs:check
+      - name: PMD
+        run: mvn pmd:check

.github/workflows/clang-format-lint.yml

@@ -9,7 +9,7 @@ jobs:
 
     steps:
     - uses: actions/checkout@v4
-    - uses: DoozyX/clang-format-lint-action@v0.17
+    - uses: DoozyX/clang-format-lint-action@v0.18
       with:
         source: './src'
         extensions: 'java'

.github/workflows/codeql.yml

@@ -26,10 +26,10 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
 
-      - name: Set up JDK 17
+      - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: 17
+          java-version: 21
           distribution: 'adopt'
 
       - name: Initialize CodeQL

.gitpod.dockerfile

@@ -1,4 +1,4 @@
-FROM gitpod/workspace-java-17:2024-04-15-14-41-42
+FROM gitpod/workspace-java-21:2024-07-14-17-19-51
 
 ENV LLVM_SCRIPT="tmp_llvm.sh"
 

DIRECTORY.md

@@ -18,6 +18,7 @@
             * [ParenthesesGenerator](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/backtracking/ParenthesesGenerator.java)
             * [Permutation](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/backtracking/Permutation.java)
             * [PowerSum](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/backtracking/PowerSum.java)
+            * [SubsequenceFinder](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/backtracking/SubsequenceFinder.java)
             * [WordSearch](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/backtracking/WordSearch.java)
           * bitmanipulation
             * [BitSwap](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/BitSwap.java)
@@ -52,6 +53,7 @@
             * [SimpleSubCipher](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/SimpleSubCipher.java)
             * [Vigenere](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/Vigenere.java)
           * conversions
+            * [AffineConverter](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/AffineConverter.java)
             * [AnyBaseToAnyBase](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/AnyBaseToAnyBase.java)
             * [AnyBaseToDecimal](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/AnyBaseToDecimal.java)
             * [AnytoAny](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/AnytoAny.java)
@@ -60,7 +62,7 @@
             * [BinaryToOctal](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/BinaryToOctal.java)
             * [DecimalToAnyBase](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/DecimalToAnyBase.java)
             * [DecimalToBinary](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/DecimalToBinary.java)
-            * [DecimalToHexaDecimal](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/DecimalToHexaDecimal.java)
+            * [DecimalToHexadecimal](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/DecimalToHexadecimal.java)
             * [DecimalToOctal](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/DecimalToOctal.java)
             * [HexaDecimalToBinary](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/HexaDecimalToBinary.java)
             * [HexaDecimalToDecimal](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/HexaDecimalToDecimal.java)
@@ -72,6 +74,8 @@
             * [RgbHsvConversion](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/RgbHsvConversion.java)
             * [RomanToInteger](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/RomanToInteger.java)
             * [TurkishToLatinConversion](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/TurkishToLatinConversion.java)
+            * [UnitConversions](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/UnitConversions.java)
+            * [UnitsConverter](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/UnitsConverter.java)
           * datastructures
             * bags
               * [Bag](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/bags/Bag.java)
@@ -96,14 +100,15 @@
             * dynamicarray
               * [DynamicArray](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/dynamicarray/DynamicArray.java)
             * graphs
-              * [A Star](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/A_Star.java)
+              * [AStar](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/AStar.java)
               * [BellmanFord](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/BellmanFord.java)
-              * [BipartiteGrapfDFS](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/BipartiteGrapfDFS.java)
+              * [BipartiteGraphDFS](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/BipartiteGraphDFS.java)
               * [BoruvkaAlgorithm](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/BoruvkaAlgorithm.java)
               * [ConnectedComponent](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/ConnectedComponent.java)
               * [Cycles](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/Cycles.java)
-              * [DIJSKSTRAS ALGORITHM](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/DIJSKSTRAS_ALGORITHM.java)
+              * [DijkstraAlgorithm](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/DijkstraAlgorithm.java)
               * [FloydWarshall](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/FloydWarshall.java)
+              * [FordFulkerson](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/FordFulkerson.java)
               * [Graphs](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/Graphs.java)
               * [HamiltonianCycle](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/HamiltonianCycle.java)
               * [KahnsAlgorithm](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/KahnsAlgorithm.java)
@@ -121,7 +126,6 @@
                 * [HashMapCuckooHashing](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/hashmap/hashing/HashMapCuckooHashing.java)
                 * [Intersection](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/hashmap/hashing/Intersection.java)
                 * [LinearProbingHashMap](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/hashmap/hashing/LinearProbingHashMap.java)
-                * [Main](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/hashmap/hashing/Main.java)
                 * [MainCuckooHashing](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/hashmap/hashing/MainCuckooHashing.java)
                 * [MajorityElement](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/hashmap/hashing/MajorityElement.java)
                 * [Map](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/hashmap/hashing/Map.java)
@@ -141,7 +145,7 @@
               * [CreateAndDetectLoop](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/lists/CreateAndDetectLoop.java)
               * [CursorLinkedList](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/lists/CursorLinkedList.java)
               * [DoublyLinkedList](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/lists/DoublyLinkedList.java)
-              * [Merge K SortedLinkedlist](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/lists/Merge_K_SortedLinkedlist.java)
+              * [MergeKSortedLinkedList](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/lists/MergeKSortedLinkedList.java)
               * [MergeSortedArrayList](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/lists/MergeSortedArrayList.java)
               * [MergeSortedSinglyLinkedList](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/lists/MergeSortedSinglyLinkedList.java)
               * [QuickSortLinkedList](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/lists/QuickSortLinkedList.java)
@@ -154,14 +158,15 @@
             * [Node](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/Node.java)
             * queues
               * [CircularQueue](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/queues/CircularQueue.java)
-              * [Deques](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/queues/Deques.java)
+              * [Deque](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/queues/Deque.java)
               * [GenericArrayListQueue](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/queues/GenericArrayListQueue.java)
               * [LinkedQueue](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/queues/LinkedQueue.java)
               * [PriorityQueues](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/queues/PriorityQueues.java)
-              * [Queues](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/queues/Queues.java)
+              * [Queue](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/queues/Queue.java)
             * stacks
               * [NodeStack](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/stacks/NodeStack.java)
               * [ReverseStack](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/stacks/ReverseStack.java)
+              * [Stack](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/stacks/Stack.java)
               * [StackArray](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/stacks/StackArray.java)
               * [StackArrayList](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/stacks/StackArrayList.java)
               * [StackOfLinkedList](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/stacks/StackOfLinkedList.java)
@@ -192,6 +197,7 @@
               * [RedBlackBST](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/trees/RedBlackBST.java)
               * [SameTreesCheck](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/trees/SameTreesCheck.java)
               * [SegmentTree](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/trees/SegmentTree.java)
+              * [SplayTree](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/trees/SplayTree.java)
               * [TreeRandomNode](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/trees/TreeRandomNode.java)
               * [TrieImp](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/trees/TrieImp.java)
               * [VerticalOrderTraversal](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/trees/VerticalOrderTraversal.java)
@@ -225,7 +231,6 @@
             * [EditDistance](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/dynamicprogramming/EditDistance.java)
             * [EggDropping](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/dynamicprogramming/EggDropping.java)
             * [Fibonacci](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/dynamicprogramming/Fibonacci.java)
-            * [FordFulkerson](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/dynamicprogramming/FordFulkerson.java)
             * [KadaneAlgorithm](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/dynamicprogramming/KadaneAlgorithm.java)
             * [Knapsack](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/dynamicprogramming/Knapsack.java)
             * [KnapsackMemoization](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/dynamicprogramming/KnapsackMemoization.java)
@@ -290,6 +295,7 @@
             * [DistanceFormula](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/DistanceFormula.java)
             * [DudeneyNumber](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/DudeneyNumber.java)
             * [EulerMethod](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/EulerMethod.java)
+            * [EulersFunction](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/EulersFunction.java)
             * [Factorial](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/Factorial.java)
             * [FactorialRecursion](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/FactorialRecursion.java)
             * [FastInverseSqrt](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/FastInverseSqrt.java)
@@ -355,6 +361,7 @@
             * [ReverseNumber](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/ReverseNumber.java)
             * [RomanNumeralUtil](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/RomanNumeralUtil.java)
             * [SecondMinMax](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/SecondMinMax.java)
+            * [SieveOfEratosthenes](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/SieveOfEratosthenes.java)
             * [SimpsonIntegration](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/SimpsonIntegration.java)
             * [SquareFreeInteger](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/SquareFreeInteger.java)
             * [SquareRootWithBabylonianMethod](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/SquareRootWithBabylonianMethod.java)
@@ -376,7 +383,7 @@
             * [ColorContrastRatio](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/misc/ColorContrastRatio.java)
             * [InverseOfMatrix](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/misc/InverseOfMatrix.java)
             * [MapReduce](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/misc/MapReduce.java)
-            * [matrixTranspose](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/misc/matrixTranspose.java)
+            * [MatrixTranspose](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/misc/MatrixTranspose.java)
             * [MedianOfMatrix](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/misc/MedianOfMatrix.java)
             * [MedianOfRunningArray](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/misc/MedianOfRunningArray.java)
             * [MedianOfRunningArrayByte](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/misc/MedianOfRunningArrayByte.java)
@@ -389,7 +396,7 @@
             * [PalindromeSinglyLinkedList](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/misc/PalindromeSinglyLinkedList.java)
             * [RangeInSortedArray](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/misc/RangeInSortedArray.java)
             * [Sort012D](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/misc/Sort012D.java)
-            * [Sparcity](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/misc/Sparcity.java)
+            * [Sparsity](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/misc/Sparsity.java)
             * [ThreeSumProblem](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/misc/ThreeSumProblem.java)
             * [TwoSumProblem](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/misc/TwoSumProblem.java)
             * [WordBoggle](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/misc/WordBoggle.java)
@@ -403,22 +410,20 @@
               * [HammingDistance](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/cn/HammingDistance.java)
             * [Conway](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/Conway.java)
             * [CountChar](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/CountChar.java)
-            * [countSetBits](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/countSetBits.java)
+            * [CountSetBits](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/CountSetBits.java)
             * [CountWords](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/CountWords.java)
             * [CRC16](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/CRC16.java)
             * [CRC32](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/CRC32.java)
             * [CRCAlgorithm](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/CRCAlgorithm.java)
             * [Damm](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/Damm.java)
             * [Dijkstra](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/Dijkstra.java)
-            * [EulersFunction](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/EulersFunction.java)
             * [FibbonaciSeries](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/FibbonaciSeries.java)
             * [FloydTriangle](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/FloydTriangle.java)
-            * [GuassLegendre](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/GuassLegendre.java)
+            * [GaussLegendre](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/GaussLegendre.java)
             * [HappyNumbersSeq](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/HappyNumbersSeq.java)
             * [Huffman](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/Huffman.java)
             * [Implementing auto completing features using trie](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/Implementing_auto_completing_features_using_trie.java)
             * [InsertDeleteInArray](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/InsertDeleteInArray.java)
-            * [KMP](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/KMP.java)
             * [KochSnowflake](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/KochSnowflake.java)
             * [Krishnamurthy](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/Krishnamurthy.java)
             * [LinearCongruentialGenerator](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/LinearCongruentialGenerator.java)
@@ -434,17 +439,13 @@
             * [PerlinNoise](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/PerlinNoise.java)
             * [PrintAMatrixInSpiralOrder](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/PrintAMatrixInSpiralOrder.java)
             * [QueueUsingTwoStacks](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/QueueUsingTwoStacks.java)
-            * [RabinKarp](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/RabinKarp.java)
             * [RemoveDuplicateFromString](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/RemoveDuplicateFromString.java)
             * [ReturnSubsequence](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/ReturnSubsequence.java)
             * [ReverseStackUsingRecursion](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/ReverseStackUsingRecursion.java)
-            * [RootPrecision](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/RootPrecision.java)
-            * [RotateMatriceBy90Degree](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/RotateMatriceBy90Degree.java)
-            * [SieveOfEratosthenes](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/SieveOfEratosthenes.java)
+            * [RotateMatrixBy90Degrees](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/RotateMatrixBy90Degrees.java)
             * [SkylineProblem](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/SkylineProblem.java)
             * [StringMatchFiniteAutomata](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/StringMatchFiniteAutomata.java)
             * [Sudoku](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/Sudoku.java)
-            * [TopKWords](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/TopKWords.java)
             * [TowerOfHanoi](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/TowerOfHanoi.java)
             * [TwoPointers](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/TwoPointers.java)
             * [Verhoeff](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/others/Verhoeff.java)
@@ -479,7 +480,7 @@
             * [RowColumnWiseSorted2dArrayBinarySearch](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/searches/RowColumnWiseSorted2dArrayBinarySearch.java)
             * [SaddlebackSearch](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/searches/SaddlebackSearch.java)
             * [SearchInARowAndColWiseSortedMatrix](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/searches/SearchInARowAndColWiseSortedMatrix.java)
-            * [sortOrderAgnosticBinarySearch](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/searches/sortOrderAgnosticBinarySearch.java)
+            * [SortOrderAgnosticBinarySearch](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/searches/SortOrderAgnosticBinarySearch.java)
             * [SquareRootBinarySearch](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/searches/SquareRootBinarySearch.java)
             * [TernarySearch](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/searches/TernarySearch.java)
             * [UnionFind](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/searches/UnionFind.java)
@@ -490,7 +491,7 @@
             * [BitonicSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/BitonicSort.java)
             * [BogoSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/BogoSort.java)
             * [BubbleSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/BubbleSort.java)
-            * [BubbleSortRecursion](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/BubbleSortRecursion.java)
+            * [BubbleSortRecursive](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/BubbleSortRecursive.java)
             * [BucketSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/BucketSort.java)
             * [CircleSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/CircleSort.java)
             * [CocktailShakerSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/CocktailShakerSort.java)
@@ -501,6 +502,7 @@
             * [DualPivotQuickSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/DualPivotQuickSort.java)
             * [DutchNationalFlagSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/DutchNationalFlagSort.java)
             * [ExchangeSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/ExchangeSort.java)
+            * [FlashSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/FlashSort.java)
             * [GnomeSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/GnomeSort.java)
             * [HeapSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/HeapSort.java)
             * [InsertionSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/InsertionSort.java)
@@ -511,22 +513,26 @@
             * [MergeSortRecursive](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/MergeSortRecursive.java)
             * [OddEvenSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/OddEvenSort.java)
             * [PancakeSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/PancakeSort.java)
+            * [PatienceSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/PatienceSort.java)
             * [PigeonholeSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/PigeonholeSort.java)
             * [QuickSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/QuickSort.java)
             * [RadixSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/RadixSort.java)
             * [SelectionSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/SelectionSort.java)
+            * [SelectionSortRecursive](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/SelectionSortRecursive.java)
             * [ShellSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/ShellSort.java)
             * [SimpleSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/SimpleSort.java)
             * [SlowSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/SlowSort.java)
             * [SortAlgorithm](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/SortAlgorithm.java)
             * [SortUtils](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/SortUtils.java)
             * [SortUtilsRandomGenerator](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/SortUtilsRandomGenerator.java)
+            * [SpreadSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/SpreadSort.java)
             * [StoogeSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/StoogeSort.java)
             * [StrandSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/StrandSort.java)
             * [SwapSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/SwapSort.java)
             * [TimSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/TimSort.java)
             * [TopologicalSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/TopologicalSort.java)
             * [TreeSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/TreeSort.java)
+            * [WaveSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/WaveSort.java)
             * [WiggleSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/WiggleSort.java)
           * stacks
             * [BalancedBrackets](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/stacks/BalancedBrackets.java)
@@ -549,14 +555,16 @@
             * [HammingDistance](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/HammingDistance.java)
             * [HorspoolSearch](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/HorspoolSearch.java)
             * [Isomorphic](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/Isomorphic.java)
+            * [KMP](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/KMP.java)
             * [LetterCombinationsOfPhoneNumber](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/LetterCombinationsOfPhoneNumber.java)
-            * [longestNonRepeativeSubstring](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/longestNonRepeativeSubstring.java)
+            * [LongestNonRepetitiveSubstring](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/LongestNonRepetitiveSubstring.java)
             * [LongestPalindromicSubstring](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/LongestPalindromicSubstring.java)
             * [Lower](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/Lower.java)
             * [MyAtoi](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/MyAtoi.java)
             * [Palindrome](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/Palindrome.java)
             * [Pangram](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/Pangram.java)
             * [PermuteString](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/PermuteString.java)
+            * [RabinKarp](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/RabinKarp.java)
             * [ReverseString](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/ReverseString.java)
             * [ReverseStringRecursive](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/ReverseStringRecursive.java)
             * [ReverseWordsInString](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/ReverseWordsInString.java)
@@ -566,7 +574,7 @@
             * [ValidParentheses](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/ValidParentheses.java)
             * [WordLadder](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/WordLadder.java)
             * zigZagPattern
-              * [zigZagPattern](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/zigZagPattern/zigZagPattern.java)
+              * [ZigZagPattern](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/zigZagPattern/ZigZagPattern.java)
   * test
     * java
       * com
@@ -578,9 +586,11 @@
             * [FloodFillTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/FloodFillTest.java)
             * [MazeRecursionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/MazeRecursionTest.java)
             * [MColoringTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/MColoringTest.java)
+            * [NQueensTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/NQueensTest.java)
             * [ParenthesesGeneratorTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/ParenthesesGeneratorTest.java)
             * [PermutationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/PermutationTest.java)
             * [PowerSumTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/PowerSumTest.java)
+            * [SubsequenceFinderTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/SubsequenceFinderTest.java)
             * [WordSearchTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/backtracking/WordSearchTest.java)
           * bitmanipulation
             * [BitSwapTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/BitSwapTest.java)
@@ -604,10 +614,14 @@
             * [SimpleSubCipherTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/SimpleSubCipherTest.java)
             * [VigenereTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/VigenereTest.java)
           * conversions
+            * [AnyBaseToDecimalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/AnyBaseToDecimalTest.java)
             * [BinaryToDecimalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/BinaryToDecimalTest.java)
             * [BinaryToHexadecimalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/BinaryToHexadecimalTest.java)
             * [BinaryToOctalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/BinaryToOctalTest.java)
-            * [DecimalToHexaDecimalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/DecimalToHexaDecimalTest.java)
+            * [DecimalToAnyBaseTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/DecimalToAnyBaseTest.java)
+            * [DecimalToBinaryTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/DecimalToBinaryTest.java)
+            * [DecimalToHexadecimalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/DecimalToHexadecimalTest.java)
+            * [DecimalToOctalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/DecimalToOctalTest.java)
             * [HexaDecimalToBinaryTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/HexaDecimalToBinaryTest.java)
             * [HexaDecimalToDecimalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/HexaDecimalToDecimalTest.java)
             * [HexToOctTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/HexToOctTest.java)
@@ -616,7 +630,11 @@
             * [OctalToDecimalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/OctalToDecimalTest.java)
             * [OctalToHexadecimalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/OctalToHexadecimalTest.java)
             * [RomanToIntegerTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/RomanToIntegerTest.java)
+            * [UnitConversionsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/UnitConversionsTest.java)
+            * [UnitsConverterTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/UnitsConverterTest.java)
           * datastructures
+            * bag
+              * [BagTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/bag/BagTest.java)
             * bloomfilter
               * [BloomFilterTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/bloomfilter/BloomFilterTest.java)
             * buffers
@@ -634,8 +652,12 @@
               * [TwoPSetTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/crdt/TwoPSetTest.java)
             * disjointsetunion
               * [DisjointSetUnionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/disjointsetunion/DisjointSetUnionTest.java)
+            * dynamicarray
+              * [DynamicArrayTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/dynamicarray/DynamicArrayTest.java)
             * graphs
               * [BoruvkaAlgorithmTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/BoruvkaAlgorithmTest.java)
+              * [DijkstraAlgorithmTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/DijkstraAlgorithmTest.java)
+              * [FordFulkersonTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/FordFulkersonTest.java)
               * [HamiltonianCycleTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/HamiltonianCycleTest.java)
               * [KosarajuTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/KosarajuTest.java)
               * [TarjansAlgorithmTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/TarjansAlgorithmTest.java)
@@ -644,6 +666,7 @@
               * hashing
                 * [GenericHashMapUsingArrayListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/hashmap/hashing/GenericHashMapUsingArrayListTest.java)
                 * [GenericHashMapUsingArrayTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/hashmap/hashing/GenericHashMapUsingArrayTest.java)
+                * [HashMapTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/hashmap/hashing/HashMapTest.java)
                 * [LinearProbingHashMapTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/hashmap/hashing/LinearProbingHashMapTest.java)
                 * [MajorityElementTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/hashmap/hashing/MajorityElementTest.java)
                 * [MapTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/hashmap/hashing/MapTest.java)
@@ -652,14 +675,23 @@
               * [FibonacciHeapTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/heaps/FibonacciHeapTest.java)
               * [LeftistHeapTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/heaps/LeftistHeapTest.java)
             * lists
+              * [CircleLinkedListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/CircleLinkedListTest.java)
               * [QuickSortLinkedListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/QuickSortLinkedListTest.java)
               * [ReverseKGroupTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/ReverseKGroupTest.java)
               * [RotateSinglyLinkedListsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/RotateSinglyLinkedListsTest.java)
               * [SinglyLinkedListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/SinglyLinkedListTest.java)
               * [SkipListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/SkipListTest.java)
             * queues
+              * [CircularQueueTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/queues/CircularQueueTest.java)
+              * [DequeTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java)
+              * [GenericArrayListQueueTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/queues/GenericArrayListQueueTest.java)
               * [LinkedQueueTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/queues/LinkedQueueTest.java)
               * [PriorityQueuesTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/queues/PriorityQueuesTest.java)
+              * [QueueTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/queues/QueueTest.java)
+            * stacks
+              * [LinkedListStackTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/stacks/LinkedListStackTest.java)
+              * [StackArrayListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/stacks/StackArrayListTest.java)
+              * [StackArrayTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/stacks/StackArrayTest.java)
             * trees
               * [BinaryTreeTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/BinaryTreeTest.java)
               * [BSTFromSortedArrayTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/BSTFromSortedArrayTest.java)
@@ -677,6 +709,7 @@
               * [PostOrderTraversalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/PostOrderTraversalTest.java)
               * [PreOrderTraversalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/PreOrderTraversalTest.java)
               * [SameTreesCheckTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/SameTreesCheckTest.java)
+              * [SplayTreeTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/SplayTreeTest.java)
               * [TreeTestUtils](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/TreeTestUtils.java)
               * [VerticalOrderTraversalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/VerticalOrderTraversalTest.java)
               * [ZigzagTraversalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/ZigzagTraversalTest.java)
@@ -684,17 +717,27 @@
             * [BinaryExponentiationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/divideandconquer/BinaryExponentiationTest.java)
             * [StrassenMatrixMultiplicationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/divideandconquer/StrassenMatrixMultiplicationTest.java)
           * dynamicprogramming
+            * [BoardPathTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/BoardPathTest.java)
             * [CatalanNumberTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/CatalanNumberTest.java)
-            * [climbStairsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/climbStairsTest.java)
+            * [ClimbStairsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/ClimbStairsTest.java)
+            * [EditDistanceTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/EditDistanceTest.java)
             * [EggDroppingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/EggDroppingTest.java)
             * [KnapsackMemoizationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/KnapsackMemoizationTest.java)
             * [KnapsackTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/KnapsackTest.java)
             * [LevenshteinDistanceTests](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/LevenshteinDistanceTests.java)
+            * [LongestAlternatingSubsequenceTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/LongestAlternatingSubsequenceTest.java)
+            * [LongestIncreasingSubsequenceTests](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/LongestIncreasingSubsequenceTests.java)
+            * [LongestPalindromicSubstringTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/LongestPalindromicSubstringTest.java)
+            * [LongestValidParenthesesTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/LongestValidParenthesesTest.java)
             * [MinimumPathSumTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/MinimumPathSumTest.java)
             * [MinimumSumPartitionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/MinimumSumPartitionTest.java)
             * [OptimalJobSchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/OptimalJobSchedulingTest.java)
+            * [PalindromicPartitioningTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/PalindromicPartitioningTest.java)
             * [PartitionProblemTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/PartitionProblemTest.java)
+            * [RegexMatchingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/RegexMatchingTest.java)
+            * [ShortestCommonSupersequenceLengthTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/ShortestCommonSupersequenceLengthTest.java)
             * [SubsetCountTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/SubsetCountTest.java)
+            * [SubsetSumTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/SubsetSumTest.java)
             * [SumOfSubsetTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/SumOfSubsetTest.java)
             * [TribonacciTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/TribonacciTest.java)
             * [UniquePathsTests](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/UniquePathsTests.java)
@@ -727,9 +770,12 @@
             * [CollatzConjectureTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/CollatzConjectureTest.java)
             * [CombinationsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/CombinationsTest.java)
             * [CrossCorrelationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/CrossCorrelationTest.java)
+            * [DeterminantOfMatrixTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/DeterminantOfMatrixTest.java)
             * [DigitalRootTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/DigitalRootTest.java)
             * [DistanceFormulaTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/DistanceFormulaTest.java)
             * [DudeneyNumberTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/DudeneyNumberTest.java)
+            * [EulersFunctionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/EulersFunctionTest.java)
+            * [FactorialRecursionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FactorialRecursionTest.java)
             * [FactorialTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FactorialTest.java)
             * [FastInverseSqrtTests](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FastInverseSqrtTests.java)
             * [FFTTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FFTTest.java)
@@ -737,6 +783,7 @@
             * [FibonacciLoopTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FibonacciLoopTest.java)
             * [FibonacciNumberCheckTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FibonacciNumberCheckTest.java)
             * [FibonacciNumberGoldenRationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FibonacciNumberGoldenRationTest.java)
+            * [FindKthNumberTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FindKthNumberTest.java)
             * [FindMaxRecursionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FindMaxRecursionTest.java)
             * [FindMaxTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FindMaxTest.java)
             * [FindMinRecursionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FindMinRecursionTest.java)
@@ -744,6 +791,7 @@
             * [FloorTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FloorTest.java)
             * [FrizzyNumberTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FrizzyNumberTest.java)
             * [GaussianTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/GaussianTest.java)
+            * [GCDRecursionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/GCDRecursionTest.java)
             * [GCDTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/GCDTest.java)
             * [GenericRootTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/GenericRootTest.java)
             * [HarshadNumberTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/HarshadNumberTest.java)
@@ -756,13 +804,17 @@
             * [LongDivisionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/LongDivisionTest.java)
             * [LucasSeriesTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/LucasSeriesTest.java)
             * [MatrixRankTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/MatrixRankTest.java)
+            * [MatrixUtilTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/MatrixUtilTest.java)
             * [MaxValueTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/MaxValueTest.java)
             * [MeansTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/MeansTest.java)
             * [MedianTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/MedianTest.java)
             * [MillerRabinPrimalityCheckTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/MillerRabinPrimalityCheckTest.java)
             * [MinValueTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/MinValueTest.java)
             * [MobiusFunctionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/MobiusFunctionTest.java)
+            * [ModeTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/ModeTest.java)
+            * [NonRepeatingElementTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/NonRepeatingElementTest.java)
             * [NthUglyNumberTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/NthUglyNumberTest.java)
+            * [NumberOfDigitsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/NumberOfDigitsTest.java)
             * [PalindromeNumberTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/PalindromeNumberTest.java)
             * [ParseIntegerTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/ParseIntegerTest.java)
             * [PascalTriangleTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/PascalTriangleTest.java)
@@ -773,12 +825,14 @@
             * [PollardRhoTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/PollardRhoTest.java)
             * [PowerOfTwoOrNotTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/PowerOfTwoOrNotTest.java)
             * [PowerUsingRecursionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/PowerUsingRecursionTest.java)
+            * [PowTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/PowTest.java)
             * [PrimeCheckTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/PrimeCheckTest.java)
             * [PrimeFactorizationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/PrimeFactorizationTest.java)
             * [PronicNumberTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/PronicNumberTest.java)
             * [PythagoreanTripleTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/PythagoreanTripleTest.java)
             * [ReverseNumberTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/ReverseNumberTest.java)
             * [SecondMinMaxTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/SecondMinMaxTest.java)
+            * [SieveOfEratosthenesTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/SieveOfEratosthenesTest.java)
             * [SquareFreeIntegerTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/SquareFreeIntegerTest.java)
             * [SquareRootwithBabylonianMethodTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/SquareRootwithBabylonianMethodTest.java)
             * [SquareRootWithNewtonRaphsonTestMethod](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/SquareRootWithNewtonRaphsonTestMethod.java)
@@ -809,12 +863,12 @@
             * [ConwayTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/ConwayTest.java)
             * [CountCharTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/CountCharTest.java)
             * [CountFriendsPairingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/CountFriendsPairingTest.java)
-            * [countSetBitsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/countSetBitsTest.java)
+            * [CountSetBitsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/CountSetBitsTest.java)
             * [CountWordsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/CountWordsTest.java)
             * [CRC16Test](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/CRC16Test.java)
             * [CRCAlgorithmTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/CRCAlgorithmTest.java)
-            * [EulersFunctionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/EulersFunctionTest.java)
             * [FirstFitCPUTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/FirstFitCPUTest.java)
+            * [FloydTriangleTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/FloydTriangleTest.java)
             * [KadaneAlogrithmTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/KadaneAlogrithmTest.java)
             * [LineSweepTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/LineSweepTest.java)
             * [LinkListSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/LinkListSortTest.java)
@@ -823,7 +877,11 @@
             * [NewManShanksPrimeTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/NewManShanksPrimeTest.java)
             * [NextFitTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/NextFitTest.java)
             * [PasswordGenTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/PasswordGenTest.java)
-            * [SieveOfEratosthenesTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/SieveOfEratosthenesTest.java)
+            * [QueueUsingTwoStacksTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/QueueUsingTwoStacksTest.java)
+            * [RemoveDuplicateFromStringTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/RemoveDuplicateFromStringTest.java)
+            * [ReturnSubsequenceTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/ReturnSubsequenceTest.java)
+            * [ReverseStackUsingRecursionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/ReverseStackUsingRecursionTest.java)
+            * [StringMatchFiniteAutomataTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/StringMatchFiniteAutomataTest.java)
             * [TestPrintMatrixInSpiralOrder](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/TestPrintMatrixInSpiralOrder.java)
             * [TwoPointersTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/TwoPointersTest.java)
             * [WorstFitCPUTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/WorstFitCPUTest.java)
@@ -845,28 +903,39 @@
             * [RabinKarpAlgorithmTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/RabinKarpAlgorithmTest.java)
             * [RecursiveBinarySearchTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/RecursiveBinarySearchTest.java)
             * [RowColumnWiseSorted2dArrayBinarySearchTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/RowColumnWiseSorted2dArrayBinarySearchTest.java)
-            * [sortOrderAgnosticBinarySearchTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/sortOrderAgnosticBinarySearchTest.java)
+            * [SortOrderAgnosticBinarySearchTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/SortOrderAgnosticBinarySearchTest.java)
             * [TestSearchInARowAndColWiseSortedMatrix](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/TestSearchInARowAndColWiseSortedMatrix.java)
           * sorts
             * [BeadSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/BeadSortTest.java)
             * [BinaryInsertionSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/BinaryInsertionSortTest.java)
+            * [BitonicSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/BitonicSortTest.java)
             * [BogoSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/BogoSortTest.java)
+            * [BubbleSortRecursiveTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/BubbleSortRecursiveTest.java)
             * [BubbleSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/BubbleSortTest.java)
             * [BucketSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/BucketSortTest.java)
+            * [CircleSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/CircleSortTest.java)
             * [CocktailShakerSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/CocktailShakerSortTest.java)
             * [CombSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/CombSortTest.java)
+            * [CountingSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/CountingSortTest.java)
+            * [CycleSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/CycleSortTest.java)
             * [DualPivotQuickSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/DualPivotQuickSortTest.java)
             * [DutchNationalFlagSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/DutchNationalFlagSortTest.java)
             * [ExchangeSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/ExchangeSortTest.java)
+            * [FlashSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/FlashSortTest.java)
             * [GnomeSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/GnomeSortTest.java)
             * [HeapSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/HeapSortTest.java)
             * [InsertionSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/InsertionSortTest.java)
             * [IntrospectiveSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/IntrospectiveSortTest.java)
+            * [MergeSortNoExtraSpaceTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/MergeSortNoExtraSpaceTest.java)
             * [MergeSortRecursiveTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/MergeSortRecursiveTest.java)
             * [MergeSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/MergeSortTest.java)
             * [OddEvenSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/OddEvenSortTest.java)
             * [PancakeSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/PancakeSortTest.java)
+            * [PatienceSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/PatienceSortTest.java)
+            * [PigeonholeSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/PigeonholeSortTest.java)
             * [QuickSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/QuickSortTest.java)
+            * [RadixSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/RadixSortTest.java)
+            * [SelectionSortRecursiveTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/SelectionSortRecursiveTest.java)
             * [SelectionSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/SelectionSortTest.java)
             * [ShellSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/ShellSortTest.java)
             * [SimpleSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/SimpleSortTest.java)
@@ -874,12 +943,24 @@
             * [SortingAlgorithmTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/SortingAlgorithmTest.java)
             * [SortUtilsRandomGeneratorTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/SortUtilsRandomGeneratorTest.java)
             * [SortUtilsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/SortUtilsTest.java)
+            * [SpreadSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/SpreadSortTest.java)
+            * [StoogeSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/StoogeSortTest.java)
             * [StrandSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/StrandSortTest.java)
+            * [SwapSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/SwapSortTest.java)
             * [TimSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/TimSortTest.java)
             * [TopologicalSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/TopologicalSortTest.java)
             * [TreeSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/TreeSortTest.java)
+            * [WaveSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/WaveSortTest.java)
             * [WiggleSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/WiggleSortTest.java)
           * stacks
+            * [BalancedBracketsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/stacks/BalancedBracketsTest.java)
+            * [DecimalToAnyUsingStackTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/stacks/DecimalToAnyUsingStackTest.java)
+            * [DuplicateBracketsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/stacks/DuplicateBracketsTest.java)
+            * [InfixToPostfixTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/stacks/InfixToPostfixTest.java)
+            * [LargestRectangleTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/stacks/LargestRectangleTest.java)
+            * [NextGreaterElementTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/stacks/NextGreaterElementTest.java)
+            * [NextSmallerElementTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/stacks/NextSmallerElementTest.java)
+            * [PostfixToInfixTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/stacks/PostfixToInfixTest.java)
             * [StackPostfixNotationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/stacks/StackPostfixNotationTest.java)
           * strings
             * [AhoCorasickTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/AhoCorasickTest.java)
@@ -892,11 +973,13 @@
             * [HorspoolSearchTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/HorspoolSearchTest.java)
             * [IsomorphicTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/IsomorphicTest.java)
             * [LetterCombinationsOfPhoneNumberTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/LetterCombinationsOfPhoneNumberTest.java)
-            * [longestNonRepeativeSubstringTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/longestNonRepeativeSubstringTest.java)
+            * [LongestNonRepetitiveSubstringTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/LongestNonRepetitiveSubstringTest.java)
+            * [LongestPalindromicSubstringTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/LongestPalindromicSubstringTest.java)
             * [LowerTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/LowerTest.java)
             * [MyAtoiTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/MyAtoiTest.java)
             * [PalindromeTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/PalindromeTest.java)
             * [PangramTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/PangramTest.java)
+            * [PermuteStringTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/PermuteStringTest.java)
             * [ReverseStringRecursiveTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/ReverseStringRecursiveTest.java)
             * [ReverseStringTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/ReverseStringTest.java)
             * [ReverseWordsInStringTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/ReverseWordsInStringTest.java)
@@ -906,4 +989,4 @@
             * [ValidParenthesesTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/ValidParenthesesTest.java)
             * [WordLadderTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/WordLadderTest.java)
             * zigZagPattern
-              * [zigZagPatternTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/zigZagPattern/zigZagPatternTest.java)
+              * [ZigZagPatternTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/zigZagPattern/ZigZagPatternTest.java)

checkstyle.xml

@@ -0,0 +1,198 @@
+<?xml version="1.0"?>
+<!DOCTYPE module PUBLIC
+          "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
+          "https://checkstyle.org/dtds/configuration_1_3.dtd">
+
+<!--
+
+  Checkstyle configuration that checks the sun coding conventions from:
+
+    - the Java Language Specification at
+      https://docs.oracle.com/javase/specs/jls/se11/html/index.html
+
+    - the Sun Code Conventions at https://www.oracle.com/java/technologies/javase/codeconventions-contents.html
+
+    - the Javadoc guidelines at
+      https://www.oracle.com/technical-resources/articles/java/javadoc-tool.html
+
+    - the JDK Api documentation https://docs.oracle.com/en/java/javase/11/
+
+    - some best practices
+
+  Checkstyle is very configurable. Be sure to read the documentation at
+  https://checkstyle.org (or in your downloaded distribution).
+
+  Most Checks are configurable, be sure to consult the documentation.
+
+  To completely disable a check, just comment it out or delete it from the file.
+  To suppress certain violations please review suppression filters.
+
+  Finally, it is worth reading the documentation.
+
+-->
+
+<module name="Checker">
+  <!--
+      If you set the basedir property below, then all reported file
+      names will be relative to the specified directory. See
+      https://checkstyle.org/config.html#Checker
+
+      <property name="basedir" value="${basedir}"/>
+  -->
+  <property name="severity" value="error"/>
+
+  <property name="fileExtensions" value="java, properties, xml"/>
+
+  <!-- Excludes all 'module-info.java' files              -->
+  <!-- See https://checkstyle.org/filefilters/index.html -->
+  <module name="BeforeExecutionExclusionFileFilter">
+    <property name="fileNamePattern" value="module\-info\.java$"/>
+  </module>
+
+  <!-- https://checkstyle.org/filters/suppressionfilter.html -->
+  <module name="SuppressionFilter">
+    <property name="file" value="${org.checkstyle.sun.suppressionfilter.config}"
+              default="checkstyle-suppressions.xml" />
+    <property name="optional" value="true"/>
+  </module>
+
+  <!-- Checks that a package-info.java file exists for each package.     -->
+  <!-- See https://checkstyle.org/checks/javadoc/javadocpackage.html#JavadocPackage -->
+  <!-- TODO <module name="JavadocPackage"/> -->
+
+  <!-- Checks whether files end with a new line.                        -->
+  <!-- See https://checkstyle.org/checks/misc/newlineatendoffile.html -->
+  <module name="NewlineAtEndOfFile"/>
+
+  <!-- Checks that property files contain the same keys.         -->
+  <!-- See https://checkstyle.org/checks/misc/translation.html -->
+  <module name="Translation"/>
+
+  <!-- Checks for Size Violations.                    -->
+  <!-- See https://checkstyle.org/checks/sizes/index.html -->
+  <!-- TODO <module name="FileLength"/> -->
+  <!-- TODO <module name="LineLength">
+    <property name="fileExtensions" value="java"/>
+  </module> -->
+
+  <!-- Checks for whitespace                               -->
+  <!-- See https://checkstyle.org/checks/whitespace/index.html -->
+  <!-- TODO <module name="FileTabCharacter"/> -->
+
+  <!-- Miscellaneous other checks.                   -->
+  <!-- See https://checkstyle.org/checks/misc/index.html -->
+  <module name="RegexpSingleline">
+    <property name="format" value="\s+$"/>
+    <property name="minimum" value="0"/>
+    <property name="maximum" value="0"/>
+    <property name="message" value="Line has trailing spaces."/>
+  </module>
+
+  <!-- Checks for Headers                                -->
+  <!-- See https://checkstyle.org/checks/header/index.html   -->
+  <!-- <module name="Header"> -->
+  <!--   <property name="headerFile" value="${checkstyle.header.file}"/> -->
+  <!--   <property name="fileExtensions" value="java"/> -->
+  <!-- </module> -->
+
+  <module name="TreeWalker">
+
+    <!-- Checks for Javadoc comments.                     -->
+    <!-- See https://checkstyle.org/checks/javadoc/index.html -->
+    <module name="InvalidJavadocPosition"/>
+    <!-- TODO <module name="JavadocMethod"/> -->
+    <!-- TODO <module name="JavadocType"/> -->
+    <!-- TODO <module name="JavadocVariable"/> -->
+    <!-- TODO <module name="JavadocStyle"/> -->
+    <!-- TODO <module name="MissingJavadocMethod"/> -->
+
+    <!-- Checks for Naming Conventions.                  -->
+    <!-- See https://checkstyle.org/checks/naming/index.html -->
+    <module name="ConstantName"/>
+    <module name="LocalFinalVariableName"/>
+    <module name="LocalVariableName"/>
+    <module name="MemberName"/>
+    <module name="MethodName"/>
+    <module name="PackageName"/>
+    <module name="ParameterName"/>
+    <module name="StaticVariableName"/>
+    <module name="TypeName"/>
+
+    <!-- Checks for imports                              -->
+    <!-- See https://checkstyle.org/checks/imports/index.html -->
+    <module name="AvoidStarImport"/>
+    <module name="IllegalImport"/> <!-- defaults to sun.* packages -->
+    <module name="RedundantImport"/>
+    <module name="UnusedImports">
+      <property name="processJavadoc" value="false"/>
+    </module>
+
+    <!-- Checks for Size Violations.                    -->
+    <!-- See https://checkstyle.org/checks/sizes/index.html -->
+    <module name="MethodLength"/>
+    <module name="ParameterNumber"/>
+
+    <!-- Checks for whitespace                               -->
+    <!-- See https://checkstyle.org/checks/whitespace/index.html -->
+    <module name="EmptyForIteratorPad"/>
+    <!-- TODO <module name="GenericWhitespace"/> -->
+    <module name="MethodParamPad"/>
+    <!-- TODO <module name="NoWhitespaceAfter"/> -->
+    <module name="NoWhitespaceBefore"/>
+    <module name="OperatorWrap"/>
+    <module name="ParenPad"/>
+    <module name="TypecastParenPad"/>
+    <module name="WhitespaceAfter"/>
+    <module name="WhitespaceAround"/>
+
+    <!-- Modifier Checks                                    -->
+    <!-- See https://checkstyle.org/checks/modifier/index.html -->
+    <module name="ModifierOrder"/>
+    <module name="RedundantModifier"/>
+
+    <!-- Checks for blocks. You know, those {}'s         -->
+    <!-- See https://checkstyle.org/checks/blocks/index.html -->
+    <module name="AvoidNestedBlocks"/>
+    <!-- TODO <module name="EmptyBlock"/> -->
+    <!-- TODO <module name="LeftCurly"/> -->
+    <module name="NeedBraces"/>
+    <!-- TODO <module name="RightCurly"/> -->
+
+    <!-- Checks for common coding problems               -->
+    <!-- See https://checkstyle.org/checks/coding/index.html -->
+    <module name="EmptyStatement"/>
+    <module name="EqualsHashCode"/>
+    <!-- TODO <module name="HiddenField"/> -->
+    <module name="IllegalInstantiation"/>
+    <module name="InnerAssignment"/>
+    <!-- TODO <module name="MagicNumber"/> -->
+    <module name="MissingSwitchDefault"/>
+    <module name="MultipleVariableDeclarations"/>
+    <module name="SimplifyBooleanExpression"/>
+    <module name="SimplifyBooleanReturn"/>
+
+    <!-- Checks for class design                         -->
+    <!-- See https://checkstyle.org/checks/design/index.html -->
+    <!-- TODO <module name="DesignForExtension"/> -->
+    <module name="FinalClass"/>
+    <module name="HideUtilityClassConstructor"/>
+    <module name="InterfaceIsType"/>
+    <!-- TODO <module name="VisibilityModifier"/> -->
+
+    <!-- Miscellaneous other checks.                   -->
+    <!-- See https://checkstyle.org/checks/misc/index.html -->
+    <module name="ArrayTypeStyle"/>
+    <!-- TODO <module name="FinalParameters"/> -->
+    <!-- TODO <module name="TodoComment"/> -->
+    <module name="UpperEll"/>
+
+    <!-- https://checkstyle.org/filters/suppressionxpathfilter.html -->
+    <module name="SuppressionXpathFilter">
+      <property name="file" value="${org.checkstyle.sun.suppressionxpathfilter.config}"
+                default="checkstyle-xpath-suppressions.xml" />
+      <property name="optional" value="true"/>
+    </module>
+
+  </module>
+
+</module>

pmd-exclude.properties

@@ -0,0 +1,90 @@
+com.thealgorithms.bitmanipulation.SingleBitOperations=UselessParentheses
+com.thealgorithms.ciphers.AffineCipher=UselessParentheses
+com.thealgorithms.ciphers.ColumnarTranspositionCipher=UnnecessaryFullyQualifiedName
+com.thealgorithms.ciphers.DES=UselessParentheses
+com.thealgorithms.ciphers.HillCipher=UselessParentheses
+com.thealgorithms.ciphers.RSA=UselessParentheses
+com.thealgorithms.conversions.AnyBaseToAnyBase=UselessParentheses
+com.thealgorithms.conversions.AnytoAny=UselessParentheses
+com.thealgorithms.conversions.HexToOct=UselessParentheses
+com.thealgorithms.conversions.IntegerToRoman=UnnecessaryFullyQualifiedName
+com.thealgorithms.datastructures.crdt.LWWElementSet=UselessParentheses
+com.thealgorithms.datastructures.crdt.Pair=UnusedPrivateField
+com.thealgorithms.datastructures.graphs.AStar=UselessParentheses
+com.thealgorithms.datastructures.graphs.AdjacencyMatrixGraph=CollapsibleIfStatements,UnnecessaryFullyQualifiedName,UselessParentheses
+com.thealgorithms.datastructures.graphs.BipartiteGraphDFS=CollapsibleIfStatements
+com.thealgorithms.datastructures.graphs.Kruskal=UselessParentheses
+com.thealgorithms.datastructures.hashmap.hashing.HashMapCuckooHashing=UselessParentheses
+com.thealgorithms.datastructures.heaps.FibonacciHeap=UselessParentheses
+com.thealgorithms.datastructures.heaps.HeapElement=UselessParentheses
+com.thealgorithms.datastructures.heaps.HeapNode=UselessParentheses
+com.thealgorithms.datastructures.lists.DoublyLinkedList=UselessParentheses
+com.thealgorithms.datastructures.lists.SearchSinglyLinkedListRecursion=UselessParentheses
+com.thealgorithms.datastructures.lists.SinglyLinkedList=UnusedLocalVariable
+com.thealgorithms.datastructures.queues.PriorityQueue=UselessParentheses
+com.thealgorithms.datastructures.stacks.NodeStack=UnnecessaryFullyQualifiedName,UnusedFormalParameter
+com.thealgorithms.datastructures.stacks.StackArray=UselessParentheses
+com.thealgorithms.datastructures.trees.CheckBinaryTreeIsValidBST=UselessParentheses
+com.thealgorithms.datastructures.trees.SegmentTree=UselessParentheses
+com.thealgorithms.devutils.nodes.LargeTreeNode=UselessParentheses
+com.thealgorithms.devutils.nodes.SimpleNode=UselessParentheses
+com.thealgorithms.devutils.nodes.SimpleTreeNode=UselessParentheses
+com.thealgorithms.devutils.nodes.TreeNode=UselessParentheses
+com.thealgorithms.divideandconquer.ClosestPair=UnnecessaryFullyQualifiedName,UselessParentheses
+com.thealgorithms.divideandconquer.Point=UselessParentheses
+com.thealgorithms.dynamicprogramming.MatrixChainMultiplication=UselessParentheses
+com.thealgorithms.dynamicprogramming.ShortestSuperSequence=UselessParentheses
+com.thealgorithms.dynamicprogramming.UniquePaths=UnnecessarySemicolon
+com.thealgorithms.dynamicprogramming.WineProblem=UselessParentheses
+com.thealgorithms.maths.BinomialCoefficient=UselessParentheses
+com.thealgorithms.maths.Complex=UselessParentheses
+com.thealgorithms.maths.DistanceFormulaTest=UnnecessaryFullyQualifiedName
+com.thealgorithms.maths.Gaussian=UselessParentheses
+com.thealgorithms.maths.GcdSolutionWrapper=UselessParentheses
+com.thealgorithms.maths.HeronsFormula=UselessParentheses
+com.thealgorithms.maths.KaprekarNumbers=UselessParentheses
+com.thealgorithms.maths.KeithNumber=UselessParentheses
+com.thealgorithms.maths.LeonardoNumber=UselessParentheses
+com.thealgorithms.maths.LinearDiophantineEquationsSolver=UselessParentheses
+com.thealgorithms.maths.MatrixUtil=UselessParentheses
+com.thealgorithms.maths.RomanNumeralUtil=UselessParentheses
+com.thealgorithms.maths.SecondMinMax=UselessParentheses
+com.thealgorithms.maths.SecondMinMaxTest=UnnecessaryFullyQualifiedName
+com.thealgorithms.maths.StandardDeviation=UselessParentheses
+com.thealgorithms.maths.SumOfArithmeticSeries=UselessParentheses
+com.thealgorithms.maths.TrinomialTriangle=UselessParentheses
+com.thealgorithms.maths.VampireNumber=CollapsibleIfStatements
+com.thealgorithms.maths.Volume=UselessParentheses
+com.thealgorithms.matrixexponentiation.Fibonacci=UnnecessaryFullyQualifiedName
+com.thealgorithms.misc.Sparsity=UselessParentheses
+com.thealgorithms.misc.ThreeSumProblem=UselessParentheses
+com.thealgorithms.misc.WordBoggle=UselessParentheses
+com.thealgorithms.others.CRC16=UselessParentheses
+com.thealgorithms.others.Damm=UnnecessaryFullyQualifiedName
+com.thealgorithms.others.Luhn=UnnecessaryFullyQualifiedName
+com.thealgorithms.others.Mandelbrot=UselessParentheses
+com.thealgorithms.others.MaximumSumOfDistinctSubarraysWithLengthK=CollapsibleIfStatements
+com.thealgorithms.others.MiniMaxAlgorithm=UselessParentheses
+com.thealgorithms.others.PageRank=UselessParentheses
+com.thealgorithms.others.PerlinNoise=UselessParentheses
+com.thealgorithms.others.QueueUsingTwoStacks=UselessParentheses
+com.thealgorithms.others.QueueWithStack=UselessParentheses
+com.thealgorithms.others.Trieac=UselessParentheses
+com.thealgorithms.others.Verhoeff=UnnecessaryFullyQualifiedName
+com.thealgorithms.searches.InterpolationSearch=UselessParentheses
+com.thealgorithms.searches.KMPSearch=UselessParentheses
+com.thealgorithms.searches.LinearSearchThread=EmptyCatchBlock
+com.thealgorithms.searches.RabinKarpAlgorithm=UselessParentheses
+com.thealgorithms.sorts.CircleSort=EmptyControlStatement
+com.thealgorithms.sorts.CombSort=UselessParentheses
+com.thealgorithms.sorts.DutchNationalFlagSort=UselessParentheses
+com.thealgorithms.sorts.LinkListSort=EmptyControlStatement,UnusedLocalVariable
+com.thealgorithms.sorts.MergeSortNoExtraSpace=UselessParentheses
+com.thealgorithms.sorts.PigeonholeSort=UselessParentheses
+com.thealgorithms.sorts.RadixSort=UselessParentheses
+com.thealgorithms.sorts.WiggleSort=UselessParentheses
+com.thealgorithms.stacks.PostfixToInfix=UselessParentheses
+com.thealgorithms.strings.HorspoolSearch=UnnecessaryFullyQualifiedName,UselessParentheses
+com.thealgorithms.strings.MyAtoi=UselessParentheses
+com.thealgorithms.strings.Palindrome=UselessParentheses
+com.thealgorithms.strings.Solution=CollapsibleIfStatements

pom.xml

@@ -10,9 +10,9 @@
 
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <maven.compiler.source>17</maven.compiler.source>
-        <maven.compiler.target>17</maven.compiler.target>
-        <assertj.version>3.25.3</assertj.version>
+        <maven.compiler.source>21</maven.compiler.source>
+        <maven.compiler.target>21</maven.compiler.target>
+        <assertj.version>3.26.3</assertj.version>
     </properties>
 
     <dependencyManagement>
@@ -20,7 +20,7 @@
             <dependency>
                 <groupId>org.junit</groupId>
                 <artifactId>junit-bom</artifactId>
-                <version>5.10.2</version>
+                <version>5.11.0</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>
@@ -31,7 +31,7 @@
         <dependency>
             <groupId>org.junit.jupiter</groupId>
             <artifactId>junit-jupiter</artifactId>
-            <version>5.10.2</version>
+            <version>5.11.0</version>
             <scope>test</scope>
         </dependency>
         <dependency>
@@ -44,18 +44,18 @@
         <dependency>
             <groupId>org.junit.jupiter</groupId>
             <artifactId>junit-jupiter-api</artifactId>
-            <version>5.10.2</version>
+            <version>5.11.0</version>
             <scope>test</scope>
         </dependency>
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-lang3</artifactId>
-            <version>3.14.0</version>
+            <version>3.17.0</version>
         </dependency>
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-collections4</artifactId>
-            <version>4.5.0-M1</version>
+            <version>4.5.0-M2</version>
         </dependency>
     </dependencies>
 
@@ -63,7 +63,7 @@
         <plugins>
             <plugin>
                 <artifactId>maven-surefire-plugin</artifactId>
-                <version>3.2.5</version>
+                <version>3.5.0</version>
                 <configuration>
                     <forkNode implementation="org.apache.maven.plugin.surefire.extensions.SurefireForkNodeFactory"/>
                 </configuration>
@@ -71,10 +71,18 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
-                <version>3.10.1</version>
+                <version>3.13.0</version>
                 <configuration>
-                    <source>17</source>
-                    <target>17</target>
+                    <source>21</source>
+                    <target>21</target>
+                    <compilerArgs>
+                        <arg>-Xlint:all</arg>
+                        <arg>-Xlint:-auxiliaryclass</arg>
+                        <arg>-Xlint:-rawtypes</arg>
+                        <arg>-Xlint:-unchecked</arg>
+                        <arg>-Xlint:-lossy-conversions</arg>
+                        <arg>-Werror</arg>
+                    </compilerArgs>
                 </configuration>
             </plugin>
             <plugin>
@@ -96,6 +104,56 @@
                     </execution>
                 </executions>
             </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-checkstyle-plugin</artifactId>
+                <version>3.5.0</version>
+                <configuration>
+                    <configLocation>checkstyle.xml</configLocation>
+                    <consoleOutput>true</consoleOutput>
+                    <includeTestSourceDirectory>true</includeTestSourceDirectory>
+                    <violationSeverity>warning</violationSeverity>
+                </configuration>
+                <dependencies>
+                    <dependency>
+                    <groupId>com.puppycrawl.tools</groupId>
+                    <artifactId>checkstyle</artifactId>
+                    <version>10.18.1</version>
+                    </dependency>
+                </dependencies>
+            </plugin>
+            <plugin>
+                <groupId>com.github.spotbugs</groupId>
+                <artifactId>spotbugs-maven-plugin</artifactId>
+                <version>4.8.6.3</version>
+                <configuration>
+                    <excludeFilterFile>spotbugs-exclude.xml</excludeFilterFile>
+                    <includeTests>true</includeTests>
+                    <plugins>
+                        <plugin>
+                            <groupId>com.mebigfatguy.fb-contrib</groupId>
+                            <artifactId>fb-contrib</artifactId>
+                            <version>7.6.4</version>
+                        </plugin>
+                        <plugin>
+                            <groupId>com.h3xstream.findsecbugs</groupId>
+                            <artifactId>findsecbugs-plugin</artifactId>
+                            <version>1.13.0</version>
+                        </plugin>
+                    </plugins>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-pmd-plugin</artifactId>
+                <version>3.25.0</version>
+                <configuration>
+                    <printFailingErrors>true</printFailingErrors>
+                    <includeTests>true</includeTests>
+                    <linkXRef>false</linkXRef>
+                    <excludeFromFailureFile>pmd-exclude.properties</excludeFromFailureFile>
+                </configuration>
+            </plugin>
         </plugins>
     </build>
 </project>

spotbugs-exclude.xml

@@ -0,0 +1,217 @@
+<FindBugsFilter>
+    <Match>
+        <Bug pattern="DM_DEFAULT_ENCODING" />
+    </Match>
+    <Match>
+        <Bug pattern="EI_EXPOSE_REP2" />
+    </Match>
+    <Match>
+        <Bug pattern="DMI_RANDOM_USED_ONLY_ONCE" />
+    </Match>
+    <Match>
+        <Bug pattern="SF_SWITCH_NO_DEFAULT" />
+    </Match>
+    <Match>
+        <Bug pattern="RV_RETURN_VALUE_IGNORED_NO_SIDE_EFFECT" />
+    </Match>
+    <Match>
+        <Bug pattern="DM_NEXTINT_VIA_NEXTDOUBLE" />
+    </Match>
+    <Match>
+        <Bug pattern="SIC_INNER_SHOULD_BE_STATIC" />
+    </Match>
+    <Match>
+        <Bug pattern="EI_EXPOSE_REP" />
+    </Match>
+    <Match>
+        <Bug pattern="EI_EXPOSE_REP" />
+    </Match>
+    <Match>
+        <Bug pattern="SBSC_USE_STRINGBUFFER_CONCATENATION" />
+    </Match>
+    <Match>
+        <Bug pattern="PA_PUBLIC_PRIMITIVE_ATTRIBUTE" />
+    </Match>
+    <Match>
+        <Bug pattern="MS_PKGPROTECT" />
+    </Match>
+    <Match>
+        <Bug pattern="SE_COMPARATOR_SHOULD_BE_SERIALIZABLE" />
+    </Match>
+    <Match>
+        <Bug pattern="INT_BAD_REM_BY_1" />
+    </Match>
+    <Match>
+        <Bug pattern="ICAST_IDIV_CAST_TO_DOUBLE" />
+    </Match>
+    <Match>
+        <Bug pattern="FE_FLOATING_POINT_EQUALITY" />
+    </Match>
+    <Match>
+        <Bug pattern="CT_CONSTRUCTOR_THROW" />
+    </Match>
+    <Match>
+        <Bug pattern="URF_UNREAD_FIELD" />
+    </Match>
+    <Match>
+        <Bug pattern="RC_REF_COMPARISON" />
+    </Match>
+    <Match>
+        <Bug pattern="MS_EXPOSE_REP" />
+    </Match>
+    <Match>
+        <Bug pattern="DM_BOXED_PRIMITIVE_FOR_PARSING" />
+    </Match>
+    <Match>
+        <Bug pattern="UWF_UNWRITTEN_FIELD" />
+    </Match>
+    <Match>
+        <Bug pattern="UWF_NULL_FIELD" />
+    </Match>
+    <Match>
+        <Bug pattern="NP_UNWRITTEN_FIELD" />
+    </Match>
+    <Match>
+        <Bug pattern="URF_UNREAD_PUBLIC_OR_PROTECTED_FIELD" />
+    </Match>
+    <Match>
+        <Bug pattern="NP_IMMEDIATE_DEREFERENCE_OF_READLINE" />
+    </Match>
+    <Match>
+        <Bug pattern="EQ_COMPARETO_USE_OBJECT_EQUALS" />
+    </Match>
+    <Match>
+        <Bug pattern="SA_FIELD_SELF_ASSIGNMENT" />
+    </Match>
+    <Match>
+        <Bug pattern="RCN_REDUNDANT_NULLCHECK_OF_NONNULL_VALUE" />
+    </Match>
+    <!-- fb-contrib -->
+    <Match>
+        <Bug pattern="OCP_OVERLY_CONCRETE_PARAMETER" />
+    </Match>
+    <Match>
+        <Bug pattern="LSC_LITERAL_STRING_COMPARISON" />
+    </Match>
+    <Match>
+        <Bug pattern="CE_CLASS_ENVY" />
+    </Match>
+    <Match>
+        <Bug pattern="PSC_PRESIZE_COLLECTIONS" />
+    </Match>
+    <Match>
+        <Bug pattern="SACM_STATIC_ARRAY_CREATED_IN_METHOD" />
+    </Match>
+    <Match>
+        <Bug pattern="LUI_USE_SINGLETON_LIST" />
+    </Match>
+    <Match>
+        <Bug pattern="CLI_CONSTANT_LIST_INDEX" />
+    </Match>
+    <Match>
+        <Bug pattern="CNC_COLLECTION_NAMING_CONFUSION" />
+    </Match>
+    <Match>
+        <Bug pattern="TR_TAIL_RECURSION" />
+    </Match>
+    <Match>
+        <Bug pattern="USBR_UNNECESSARY_STORE_BEFORE_RETURN" />
+    </Match>
+    <Match>
+        <Bug pattern="BL_BURYING_LOGIC" />
+    </Match>
+    <Match>
+        <Bug pattern="PCOA_PARTIALLY_CONSTRUCTED_OBJECT_ACCESS" />
+    </Match>
+    <Match>
+        <Bug pattern="UTWR_USE_TRY_WITH_RESOURCES" />
+    </Match>
+    <Match>
+        <Bug pattern="MUI_CONTAINSKEY_BEFORE_GET" />
+    </Match>
+    <Match>
+        <Bug pattern="IMC_IMMATURE_CLASS_PRINTSTACKTRACE" />
+    </Match>
+    <Match>
+        <Bug pattern="UCPM_USE_CHARACTER_PARAMETERIZED_METHOD" />
+    </Match>
+    <Match>
+        <Bug pattern="SUA_SUSPICIOUS_UNINITIALIZED_ARRAY" />
+    </Match>
+    <Match>
+        <Bug pattern="SPP_USE_MATH_CONSTANT" />
+    </Match>
+    <Match>
+        <Bug pattern="UJM_UNJITABLE_METHOD" />
+    </Match>
+    <Match>
+        <Bug pattern="SEC_SIDE_EFFECT_CONSTRUCTOR" />
+    </Match>
+    <Match>
+        <Bug pattern="MDM_STRING_BYTES_ENCODING" />
+    </Match>
+    <Match>
+        <Bug pattern="PMB_POSSIBLE_MEMORY_BLOAT" />
+    </Match>
+    <Match>
+        <Bug pattern="LSYC_LOCAL_SYNCHRONIZED_COLLECTION" />
+    </Match>
+    <Match>
+        <Bug pattern="IOI_USE_OF_FILE_STREAM_CONSTRUCTORS" />
+    </Match>
+    <Match>
+        <Bug pattern="UP_UNUSED_PARAMETER" />
+    </Match>
+    <Match>
+        <Bug pattern="DSOC_DUBIOUS_SET_OF_COLLECTIONS" />
+    </Match>
+    <Match>
+        <Bug pattern="NAB_NEEDLESS_BOX_TO_UNBOX" />
+    </Match>
+    <Match>
+        <Bug pattern="FPL_FLOATING_POINT_LOOPS" />
+    </Match>
+    <Match>
+        <Bug pattern="ITU_INAPPROPRIATE_TOSTRING_USE" />
+    </Match>
+    <Match>
+        <Bug pattern="SPP_PASSING_THIS_AS_PARM" />
+    </Match>
+    <Match>
+        <Bug pattern="FCBL_FIELD_COULD_BE_LOCAL" />
+    </Match>
+    <Match>
+        <Bug pattern="CFS_CONFUSING_FUNCTION_SEMANTICS" />
+    </Match>
+    <Match>
+        <Bug pattern="PRMC_POSSIBLY_REDUNDANT_METHOD_CALLS" />
+    </Match>
+    <Match>
+        <Bug pattern="FCCD_FIND_CLASS_CIRCULAR_DEPENDENCY" />
+    </Match>
+    <Match>
+        <Bug pattern="PL_PARALLEL_LISTS" />
+    </Match>
+    <Match>
+        <Bug pattern="PCAIL_POSSIBLE_CONSTANT_ALLOCATION_IN_LOOP" />
+    </Match>
+    <Match>
+        <Bug pattern="STT_STRING_PARSING_A_FIELD" />
+    </Match>
+    <Match>
+        <Bug pattern="IMC_IMMATURE_CLASS_BAD_SERIALVERSIONUID" />
+    </Match>
+    <Match>
+        <Bug pattern="DRE_DECLARED_RUNTIME_EXCEPTION" />
+    </Match>
+    <Match>
+        <Bug pattern="SLS_SUSPICIOUS_LOOP_SEARCH" />
+    </Match>
+    <!-- find-sec-bugs -->
+    <Match>
+        <Bug pattern="PREDICTABLE_RANDOM" />
+    </Match>
+    <Match>
+        <Bug pattern="HARD_CODE_KEY" />
+    </Match>
+</FindBugsFilter>

src/main/java/com/thealgorithms/backtracking/AllPathsFromSourceToTarget.java

@@ -1,15 +1,14 @@
-/**
- * Author : Siddhant Swarup Mallick
- * Github : https://github.com/siddhant2002
- */
-
-/** Program description - To find all possible paths from source to destination*/
-
-/**Wikipedia link -> https://en.wikipedia.org/wiki/Shortest_path_problem */
 package com.thealgorithms.backtracking;
 
-import java.util.*;
+import java.util.ArrayList;
+import java.util.List;
 
+/**
+ * Program description - To find all possible paths from source to destination
+ * <a href="https://en.wikipedia.org/wiki/Shortest_path_problem">Wikipedia</a>
+ *
+ * @author <a href="https://github.com/siddhant2002">Siddhant Swarup Mallick</a>
+ */
 public class AllPathsFromSourceToTarget {
 
     // No. of vertices in graph

src/main/java/com/thealgorithms/backtracking/ArrayCombination.java

@@ -1,29 +1,42 @@
 package com.thealgorithms.backtracking;
 
-import java.util.*;
+import java.util.ArrayList;
+import java.util.List;
 
 /**
- * Finds all permutations of 1...n of length k
- * @author TheClerici (<a href="https://github.com/TheClerici">git-TheClerici</a>)
+ * Finds all combinations of 0...n-1 of length k
  */
-public class ArrayCombination {
-    private static int length;
+public final class ArrayCombination {
+    private ArrayCombination() {
+    }
 
     /**
-     * Find all combinations of 1..n by creating an array and using backtracking in Combination.java
-     * @param n max value of the array.
-     * @param k length of combination
-     * @return a list of all combinations of length k. If k == 0, return null.
+     * Finds all combinations of length k of 0..n-1 using backtracking.
+     *
+     * @param n Number of the elements.
+     * @param k Length of the combination.
+     * @return A list of all combinations of length k.
      */
-    public static List<TreeSet<Integer>> combination(int n, int k) {
-        if (n <= 0) {
-            return null;
+    public static List<List<Integer>> combination(int n, int k) {
+        if (n < 0 || k < 0 || k > n) {
+            throw new IllegalArgumentException("Wrong input.");
         }
-        length = k;
-        Integer[] arr = new Integer[n];
-        for (int i = 1; i <= n; i++) {
-            arr[i - 1] = i;
+
+        List<List<Integer>> combinations = new ArrayList<>();
+        combine(combinations, new ArrayList<>(), 0, n, k);
+        return combinations;
+    }
+
+    private static void combine(List<List<Integer>> combinations, List<Integer> current, int start, int n, int k) {
+        if (current.size() == k) { // Base case: combination found
+            combinations.add(new ArrayList<>(current)); // Copy to avoid modification
+            return;
+        }
+
+        for (int i = start; i < n; i++) {
+            current.add(i);
+            combine(combinations, current, i + 1, n, k);
+            current.removeLast(); // Backtrack
         }
-        return Combination.combination(arr, length);
     }
 }

src/main/java/com/thealgorithms/backtracking/Combination.java

@@ -1,12 +1,17 @@
 package com.thealgorithms.backtracking;
 
-import java.util.*;
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.TreeSet;
 
 /**
  * Finds all permutations of given array
  * @author Alan Piao (<a href="https://github.com/cpiao3">git-Alan Piao</a>)
  */
-public class Combination {
+public final class Combination {
+    private Combination() {
+    }
 
     private static int length;
 
@@ -38,7 +43,9 @@ public class Combination {
      * @param <T> the type of elements in the array.
      */
     private static <T> void backtracking(T[] arr, int index, TreeSet<T> currSet, List<TreeSet<T>> result) {
-        if (index + length - currSet.size() > arr.length) return;
+        if (index + length - currSet.size() > arr.length) {
+            return;
+        }
         if (length - 1 == currSet.size()) {
             for (int i = index; i < arr.length; i++) {
                 currSet.add(arr[i]);

src/main/java/com/thealgorithms/backtracking/KnightsTour.java

@@ -1,6 +1,8 @@
 package com.thealgorithms.backtracking;
 
-import java.util.*;
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.List;
 
 /*
     * Problem Statement: -
@@ -24,10 +26,12 @@ import java.util.*;
         51  46  55  44  53   4  21  12
 
  */
-public class KnightsTour {
+public final class KnightsTour {
+    private KnightsTour() {
+    }
 
-    private static final int base = 12;
-    private static final int[][] moves = {
+    private static final int BASE = 12;
+    private static final int[][] MOVES = {
         {1, -2},
         {2, -1},
         {2, 1},
@@ -41,19 +45,19 @@ public class KnightsTour {
     private static int total; // total squares in chess
 
     public static void main(String[] args) {
-        grid = new int[base][base];
-        total = (base - 4) * (base - 4);
+        grid = new int[BASE][BASE];
+        total = (BASE - 4) * (BASE - 4);
 
-        for (int r = 0; r < base; r++) {
-            for (int c = 0; c < base; c++) {
-                if (r < 2 || r > base - 3 || c < 2 || c > base - 3) {
+        for (int r = 0; r < BASE; r++) {
+            for (int c = 0; c < BASE; c++) {
+                if (r < 2 || r > BASE - 3 || c < 2 || c > BASE - 3) {
                     grid[r][c] = -1;
                 }
             }
         }
 
-        int row = 2 + (int) (Math.random() * (base - 4));
-        int col = 2 + (int) (Math.random() * (base - 4));
+        int row = 2 + (int) (Math.random() * (BASE - 4));
+        int col = 2 + (int) (Math.random() * (BASE - 4));
 
         grid[row][col] = 1;
 
@@ -95,7 +99,7 @@ public class KnightsTour {
     private static List<int[]> neighbors(int row, int column) {
         List<int[]> neighbour = new ArrayList<>();
 
-        for (int[] m : moves) {
+        for (int[] m : MOVES) {
             int x = m[0];
             int y = m[1];
             if (grid[row + y][column + x] == 0) {
@@ -109,7 +113,7 @@ public class KnightsTour {
     // Returns the total count of neighbors
     private static int countNeighbors(int row, int column) {
         int num = 0;
-        for (int[] m : moves) {
+        for (int[] m : MOVES) {
             if (grid[row + m[1]][column + m[0]] == 0) {
                 num++;
             }

src/main/java/com/thealgorithms/backtracking/MColoring.java

@@ -1,6 +1,10 @@
 package com.thealgorithms.backtracking;
 
-import java.util.*;
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.LinkedList;
+import java.util.Queue;
+import java.util.Set;
 
 /**
  * @author Bama Charan Chhandogi (https://github.com/BamaCharanChhandogi)
@@ -10,7 +14,9 @@ class Node {
     Set<Integer> edges = new HashSet<Integer>();
 }
 
-public class MColoring {
+public final class MColoring {
+    private MColoring() {
+    }
     static int possiblePaint(ArrayList<Node> nodes, int n, int m) {
 
         // Create a visited array of n nodes
@@ -53,7 +59,9 @@ public class MColoring {
                     // If number of colors used exceeds m,
                     // return 0
                     maxColors = Math.max(maxColors, Math.max(nodes.get(top).color, nodes.get(it).color));
-                    if (maxColors > m) return 0;
+                    if (maxColors > m) {
+                        return 0;
+                    }
 
                     // If the adjacent node is not visited,
                     // mark it visited and push it in queue

src/main/java/com/thealgorithms/backtracking/MazeRecursion.java

@@ -1,6 +1,8 @@
 package com.thealgorithms.backtracking;
 
-public class MazeRecursion {
+public final class MazeRecursion {
+    private MazeRecursion() {
+    }
 
     public static void mazeRecursion() {
         // First create a 2 dimensions array to mimic a maze map

src/main/java/com/thealgorithms/backtracking/NQueens.java

@@ -32,15 +32,14 @@ import java.util.List;
  * queen is not placed safely. If there is no such way then return an empty list
  * as solution
  */
-public class NQueens {
+public final class NQueens {
+    private NQueens() {
+    }
 
-    public static void main(String[] args) {
-        placeQueens(1);
-        placeQueens(2);
-        placeQueens(3);
-        placeQueens(4);
-        placeQueens(5);
-        placeQueens(6);
+    public static List<List<String>> getNQueensArrangements(int queens) {
+        List<List<String>> arrangements = new ArrayList<>();
+        getSolution(queens, arrangements, new int[queens], 0);
+        return arrangements;
     }
 
     public static void placeQueens(final int queens) {

src/main/java/com/thealgorithms/backtracking/ParenthesesGenerator.java

@@ -19,7 +19,7 @@ public final class ParenthesesGenerator {
      */
     public static List<String> generateParentheses(final int n) {
         if (n < 0) {
-            throw new IllegalArgumentException("The number of pairs of parentheses cannot be nagative");
+            throw new IllegalArgumentException("The number of pairs of parentheses cannot be negative");
         }
         List<String> result = new ArrayList<>();
         generateParenthesesHelper(result, "", 0, 0, n);

src/main/java/com/thealgorithms/backtracking/Permutation.java

@@ -7,7 +7,9 @@ import java.util.List;
  * Finds all permutations of given array
  * @author Alan Piao (<a href="https://github.com/cpiao3">Git-Alan Piao</a>)
  */
-public class Permutation {
+public final class Permutation {
+    private Permutation() {
+    }
 
     /**
      * Find all permutations of given array using backtracking

src/main/java/com/thealgorithms/backtracking/PowerSum.java

@@ -8,32 +8,33 @@ package com.thealgorithms.backtracking;
  */
 public class PowerSum {
 
-    private int count = 0, sum = 0;
+    private int count = 0;
+    private int sum = 0;
 
-    public int powSum(int N, int X) {
-        Sum(N, X, 1);
+    public int powSum(int n, int x) {
+        sum(n, x, 1);
         return count;
     }
 
     // here i is the natural number which will be raised by X and added in sum.
-    public void Sum(int N, int X, int i) {
+    public void sum(int n, int x, int i) {
         // if sum is equal to N that is one of our answer and count is increased.
-        if (sum == N) {
+        if (sum == n) {
             count++;
             return;
         } // we will be adding next natural number raised to X only if on adding it in sum the
           // result is less than N.
-        else if (sum + power(i, X) <= N) {
-            sum += power(i, X);
-            Sum(N, X, i + 1);
+        else if (sum + power(i, x) <= n) {
+            sum += power(i, x);
+            sum(n, x, i + 1);
             // backtracking and removing the number added last since no possible combination is
             // there with it.
-            sum -= power(i, X);
+            sum -= power(i, x);
         }
-        if (power(i, X) < N) {
+        if (power(i, x) < n) {
             // calling the sum function with next natural number after backtracking if when it is
             // raised to X is still less than X.
-            Sum(N, X, i + 1);
+            sum(n, x, i + 1);
         }
     }
 

src/main/java/com/thealgorithms/backtracking/SubsequenceFinder.java

@@ -0,0 +1,54 @@
+package com.thealgorithms.backtracking;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Class generates all subsequences for a given list of elements using backtracking
+ */
+public final class SubsequenceFinder {
+    private SubsequenceFinder() {
+    }
+
+    /**
+     * Find all subsequences of given list using backtracking
+     *
+     * @param sequence a list of items on the basis of which we need to generate all subsequences
+     * @param <T> the type of elements in the array
+     * @return a list of all subsequences
+     */
+    public static <T> List<List<T>> generateAll(List<T> sequence) {
+        List<List<T>> allSubSequences = new ArrayList<>();
+        if (sequence.isEmpty()) {
+            allSubSequences.add(new ArrayList<>());
+            return allSubSequences;
+        }
+        List<T> currentSubsequence = new ArrayList<>();
+        backtrack(sequence, currentSubsequence, 0, allSubSequences);
+        return allSubSequences;
+    }
+
+    /**
+     * Iterate through each branch of states
+     * We know that each state has exactly two branching
+     * It terminates when it reaches the end of the given sequence
+     *
+     * @param sequence all elements
+     * @param currentSubsequence current subsequence
+     * @param index current index
+     * @param allSubSequences contains all sequences
+     * @param <T> the type of elements which we generate
+     */
+    private static <T> void backtrack(List<T> sequence, List<T> currentSubsequence, final int index, List<List<T>> allSubSequences) {
+        assert index <= sequence.size();
+        if (index == sequence.size()) {
+            allSubSequences.add(new ArrayList<>(currentSubsequence));
+            return;
+        }
+
+        backtrack(sequence, currentSubsequence, index + 1, allSubSequences);
+        currentSubsequence.add(sequence.get(index));
+        backtrack(sequence, currentSubsequence, index + 1, allSubSequences);
+        currentSubsequence.removeLast();
+    }
+}

src/main/java/com/thealgorithms/backtracking/WordSearch.java

@@ -51,7 +51,9 @@ public class WordSearch {
             int yi = y + dy[i];
             if (isValid(xi, yi) && board[xi][yi] == word.charAt(nextIdx) && !visited[xi][yi]) {
                 boolean exists = doDFS(xi, yi, nextIdx + 1);
-                if (exists) return true;
+                if (exists) {
+                    return true;
+                }
             }
         }
         visited[x][y] = false;
@@ -66,7 +68,9 @@ public class WordSearch {
                 if (board[i][j] == word.charAt(0)) {
                     visited = new boolean[board.length][board[0].length];
                     boolean exists = doDFS(i, j, 1);
-                    if (exists) return true;
+                    if (exists) {
+                        return true;
+                    }
                 }
             }
         }

src/main/java/com/thealgorithms/bitmanipulation/HighestSetBit.java

@@ -12,7 +12,7 @@ public final class HighestSetBit {
     private HighestSetBit() {
     }
 
-    public final static Optional<Integer> findHighestSetBit(int num) {
+    public static Optional<Integer> findHighestSetBit(int num) {
         if (num < 0) {
             throw new IllegalArgumentException("Input cannot be negative");
         }

src/main/java/com/thealgorithms/bitmanipulation/IndexOfRightMostSetBit.java

@@ -5,7 +5,9 @@ package com.thealgorithms.bitmanipulation;
  * @author Bama Charan Chhandogi (https://github.com/BamaCharanChhandogi)
  */
 
-public class IndexOfRightMostSetBit {
+public final class IndexOfRightMostSetBit {
+    private IndexOfRightMostSetBit() {
+    }
     public static int indexOfRightMostSetBit(int n) {
         if (n == 0) {
             return -1; // No set bits

src/main/java/com/thealgorithms/bitmanipulation/IsEven.java

@@ -5,7 +5,9 @@ package com.thealgorithms.bitmanipulation;
  * @author Bama Charan Chhandogi (https://github.com/BamaCharanChhandogi)
  */
 
-public class IsEven {
+public final class IsEven {
+    private IsEven() {
+    }
     public static boolean isEven(int number) {
         return (number & 1) == 0;
     }

src/main/java/com/thealgorithms/bitmanipulation/IsPowerTwo.java

@@ -5,7 +5,9 @@ package com.thealgorithms.bitmanipulation;
  * @author Bama Charan Chhandogi (https://github.com/BamaCharanChhandogi)
  */
 
-public class IsPowerTwo {
+public final class IsPowerTwo {
+    private IsPowerTwo() {
+    }
     public static boolean isPowerTwo(int number) {
         if (number <= 0) {
             return false;

src/main/java/com/thealgorithms/bitmanipulation/NonRepeatingNumberFinder.java

@@ -5,7 +5,9 @@ package com.thealgorithms.bitmanipulation;
  * @author Bama Charan Chhandogi (https://github.com/BamaCharanChhandogi)
  */
 
-public class NonRepeatingNumberFinder {
+public final class NonRepeatingNumberFinder {
+    private NonRepeatingNumberFinder() {
+    }
 
     public static int findNonRepeatingNumber(int[] arr) {
         int result = 0;

src/main/java/com/thealgorithms/bitmanipulation/NumbersDifferentSigns.java

@@ -5,7 +5,9 @@ package com.thealgorithms.bitmanipulation;
  * @author Bama Charan Chhandogi
  */
 
-public class NumbersDifferentSigns {
+public final class NumbersDifferentSigns {
+    private NumbersDifferentSigns() {
+    }
 
     public static boolean differentSigns(int num1, int num2) {
         return (num1 ^ num2) < 0;

src/main/java/com/thealgorithms/bitmanipulation/ReverseBits.java

@@ -5,7 +5,9 @@ package com.thealgorithms.bitmanipulation;
  * @author Bama Charan Chhandogi
  */
 
-public class ReverseBits {
+public final class ReverseBits {
+    private ReverseBits() {
+    }
 
     public static int reverseBits(int n) {
         int result = 0;

src/main/java/com/thealgorithms/ciphers/AES.java

@@ -7,7 +7,9 @@ import java.util.Scanner;
  * This class is build to demonstrate the application of the AES-algorithm on a
  * single 128-Bit block of data.
  */
-public class AES {
+public final class AES {
+    private AES() {
+    }
 
     /**
      * Precalculated values for x to the power of 2 in Rijndaels galois field.
@@ -2754,8 +2756,8 @@ public class AES {
                     in = input.nextLine();
                     BigInteger encryptionKey = new BigInteger(in, 16);
                     System.out.println(
-                        "The encrypted message is: \n" +
-                        encrypt(plaintext, encryptionKey).toString(16)
+                        "The encrypted message is: \n"
+                        + encrypt(plaintext, encryptionKey).toString(16)
                     );
                 }
                 case 'D', 'd' -> {
@@ -2770,8 +2772,8 @@ public class AES {
                     in = input.nextLine();
                     BigInteger decryptionKey = new BigInteger(in, 16);
                     System.out.println(
-                        "The deciphered message is:\n" +
-                        decrypt(ciphertext, decryptionKey).toString(16)
+                        "The deciphered message is:\n"
+                        + decrypt(ciphertext, decryptionKey).toString(16)
                     );
                 }
                 default -> System.out.println("** End **");

src/main/java/com/thealgorithms/ciphers/AESEncryption.java

@@ -3,7 +3,12 @@ package com.thealgorithms.ciphers;
 import java.security.InvalidAlgorithmParameterException;
 import java.security.InvalidKeyException;
 import java.security.NoSuchAlgorithmException;
-import javax.crypto.*;
+import javax.crypto.BadPaddingException;
+import javax.crypto.Cipher;
+import javax.crypto.IllegalBlockSizeException;
+import javax.crypto.KeyGenerator;
+import javax.crypto.NoSuchPaddingException;
+import javax.crypto.SecretKey;
 import javax.crypto.spec.GCMParameterSpec;
 
 /**
@@ -12,7 +17,9 @@ import javax.crypto.spec.GCMParameterSpec;
  * hence in the following program we display it in hexadecimal format of the
  * underlying bytes.
  */
-public class AESEncryption {
+public final class AESEncryption {
+    private AESEncryption() {
+    }
 
     private static final char[] HEX_ARRAY = "0123456789ABCDEF".toCharArray();
     private static Cipher aesCipher;

src/main/java/com/thealgorithms/ciphers/AffineCipher.java

@@ -1,6 +1,8 @@
 package com.thealgorithms.ciphers;
 
-class AffineCipher {
+final class AffineCipher {
+    private AffineCipher() {
+    }
 
     // Key values of a and b
     static int a = 17;
@@ -25,7 +27,7 @@ class AffineCipher {
 
     static String decryptCipher(String cipher) {
         String msg = "";
-        int a_inv = 0;
+        int aInv = 0;
         int flag = 0;
 
         // Find a^-1 (the multiplicative inverse of a
@@ -36,7 +38,7 @@ class AffineCipher {
             // Check if (a*i)%26 == 1,
             // then i will be the multiplicative inverse of a
             if (flag == 1) {
-                a_inv = i;
+                aInv = i;
             }
         }
         for (int i = 0; i < cipher.length(); i++) {
@@ -44,7 +46,7 @@ class AffineCipher {
             {here x is cipher[i] and m is 26} and added 'A'
             to bring it in range of ASCII alphabet[ 65-90 | A-Z ] */
             if (cipher.charAt(i) != ' ') {
-                msg = msg + (char) (((a_inv * ((cipher.charAt(i) + 'A' - b)) % 26)) + 'A');
+                msg = msg + (char) (((aInv * ((cipher.charAt(i) + 'A' - b)) % 26)) + 'A');
             } else { // else simply append space character
                 msg += cipher.charAt(i);
             }

src/main/java/com/thealgorithms/ciphers/Blowfish.java

@@ -11,7 +11,7 @@ package com.thealgorithms.ciphers;
 public class Blowfish {
 
     // Initializing substitution boxes
-    String[][] S = {
+    String[][] sBox = {
         {
             "d1310ba6",
             "98dfb5ac",
@@ -1047,7 +1047,7 @@ public class Blowfish {
     };
 
     // Initializing subkeys with digits of pi
-    String[] P = {
+    String[] subKeys = {
         "243f6a88",
         "85a308d3",
         "13198a2e",
@@ -1104,7 +1104,9 @@ public class Blowfish {
     private String binToHex(String binary) {
         long num = Long.parseUnsignedLong(binary, 2);
         String hex = Long.toHexString(num);
-        while (hex.length() < (binary.length() / 4)) hex = "0" + hex;
+        while (hex.length() < (binary.length() / 4)) {
+            hex = "0" + hex;
+        }
 
         return hex;
     }
@@ -1120,7 +1122,9 @@ public class Blowfish {
         a = hexToBin(a);
         b = hexToBin(b);
         String ans = "";
-        for (int i = 0; i < a.length(); i++) ans += (char) (((a.charAt(i) - '0') ^ (b.charAt(i) - '0')) + '0');
+        for (int i = 0; i < a.length(); i++) {
+            ans += (char) (((a.charAt(i) - '0') ^ (b.charAt(i) - '0')) + '0');
+        }
         ans = binToHex(ans);
         return ans;
     }
@@ -1154,7 +1158,7 @@ public class Blowfish {
         for (int i = 0; i < 8; i += 2) {
             // column number for S-box is a 8-bit value
             long col = Long.parseUnsignedLong(hexToBin(plainText.substring(i, i + 2)), 2);
-            a[i / 2] = S[i / 2][(int) col];
+            a[i / 2] = sBox[i / 2][(int) col];
         }
         ans = addBin(a[0], a[1]);
         ans = xor(ans, a[2]);
@@ -1165,9 +1169,9 @@ public class Blowfish {
     // generate subkeys
     private void keyGenerate(String key) {
         int j = 0;
-        for (int i = 0; i < P.length; i++) {
+        for (int i = 0; i < subKeys.length; i++) {
             // XOR-ing 32-bit parts of the key with initial subkeys
-            P[i] = xor(P[i], key.substring(j, j + 8));
+            subKeys[i] = xor(subKeys[i], key.substring(j, j + 8));
 
             j = (j + 8) % key.length();
         }
@@ -1175,10 +1179,11 @@ public class Blowfish {
 
     // round function
     private String round(int time, String plainText) {
-        String left, right;
+        String left;
+        String right;
         left = plainText.substring(0, 8);
         right = plainText.substring(8, 16);
-        left = xor(left, P[time]);
+        left = xor(left, subKeys[time]);
 
         // output from F function
         String fOut = f(left);
@@ -1201,13 +1206,15 @@ public class Blowfish {
         // generating key
         keyGenerate(key);
 
-        for (int i = 0; i < 16; i++) plainText = round(i, plainText);
+        for (int i = 0; i < 16; i++) {
+            plainText = round(i, plainText);
+        }
 
         // postprocessing
         String right = plainText.substring(0, 8);
         String left = plainText.substring(8, 16);
-        right = xor(right, P[16]);
-        left = xor(left, P[17]);
+        right = xor(right, subKeys[16]);
+        left = xor(left, subKeys[17]);
         return left + right;
     }
 
@@ -1223,13 +1230,15 @@ public class Blowfish {
         // generating key
         keyGenerate(key);
 
-        for (int i = 17; i > 1; i--) cipherText = round(i, cipherText);
+        for (int i = 17; i > 1; i--) {
+            cipherText = round(i, cipherText);
+        }
 
         // postprocessing
         String right = cipherText.substring(0, 8);
         String left = cipherText.substring(8, 16);
-        right = xor(right, P[1]);
-        left = xor(left, P[0]);
+        right = xor(right, subKeys[1]);
+        left = xor(left, subKeys[0]);
         return left + right;
     }
 }

src/main/java/com/thealgorithms/ciphers/ColumnarTranspositionCipher.java

@@ -7,7 +7,9 @@ import java.util.Objects;
  *
  * @author <a href="https://github.com/freitzzz">freitzzz</a>
  */
-public class ColumnarTranspositionCipher {
+public final class ColumnarTranspositionCipher {
+    private ColumnarTranspositionCipher() {
+    }
 
     private static String keyword;
     private static Object[][] table;

src/main/java/com/thealgorithms/ciphers/DES.java

@@ -8,7 +8,7 @@ package com.thealgorithms.ciphers;
 public class DES {
 
     private String key;
-    private String subKeys[];
+    private final String[] subKeys;
 
     private void sanitize(String key) {
         int length = key.length();
@@ -32,66 +32,68 @@ public class DES {
         this.key = key;
     }
 
-    // Permutation table to convert initial 64 bit key to 56 bit key
-    private static int[] PC1 = {57, 49, 41, 33, 25, 17, 9, 1, 58, 50, 42, 34, 26, 18, 10, 2, 59, 51, 43, 35, 27, 19, 11, 3, 60, 52, 44, 36, 63, 55, 47, 39, 31, 23, 15, 7, 62, 54, 46, 38, 30, 22, 14, 6, 61, 53, 45, 37, 29, 21, 13, 5, 28, 20, 12, 4};
+    // Permutation table to convert initial 64-bit key to 56 bit key
+    private static final int[] PC1 = {57, 49, 41, 33, 25, 17, 9, 1, 58, 50, 42, 34, 26, 18, 10, 2, 59, 51, 43, 35, 27, 19, 11, 3, 60, 52, 44, 36, 63, 55, 47, 39, 31, 23, 15, 7, 62, 54, 46, 38, 30, 22, 14, 6, 61, 53, 45, 37, 29, 21, 13, 5, 28, 20, 12, 4};
 
     // Lookup table used to shift the initial key, in order to generate the subkeys
-    private static int[] KEY_SHIFTS = {1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1};
+    private static final int[] KEY_SHIFTS = {1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1};
 
     // Table to convert the 56 bit subkeys to 48 bit subkeys
-    private static int[] PC2 = {14, 17, 11, 24, 1, 5, 3, 28, 15, 6, 21, 10, 23, 19, 12, 4, 26, 8, 16, 7, 27, 20, 13, 2, 41, 52, 31, 37, 47, 55, 30, 40, 51, 45, 33, 48, 44, 49, 39, 56, 34, 53, 46, 42, 50, 36, 29, 32};
+    private static final int[] PC2 = {14, 17, 11, 24, 1, 5, 3, 28, 15, 6, 21, 10, 23, 19, 12, 4, 26, 8, 16, 7, 27, 20, 13, 2, 41, 52, 31, 37, 47, 55, 30, 40, 51, 45, 33, 48, 44, 49, 39, 56, 34, 53, 46, 42, 50, 36, 29, 32};
 
-    // Initial permutatation of each 64 but message block
-    private static int[] IP = {58, 50, 42, 34, 26, 18, 10, 2, 60, 52, 44, 36, 28, 20, 12, 4, 62, 54, 46, 38, 30, 22, 14, 6, 64, 56, 48, 40, 32, 24, 16, 8, 57, 49, 41, 33, 25, 17, 9, 1, 59, 51, 43, 35, 27, 19, 11, 3, 61, 53, 45, 37, 29, 21, 13, 5, 63, 55, 47, 39, 31, 23, 15, 7};
+    // Initial permutation of each 64 but message block
+    private static final int[] IP = {58, 50, 42, 34, 26, 18, 10, 2, 60, 52, 44, 36, 28, 20, 12, 4, 62, 54, 46, 38, 30, 22, 14, 6, 64, 56, 48, 40, 32, 24, 16, 8, 57, 49, 41, 33, 25, 17, 9, 1, 59, 51, 43, 35, 27, 19, 11, 3, 61, 53, 45, 37, 29, 21, 13, 5, 63, 55, 47, 39, 31, 23, 15, 7};
 
     // Expansion table to convert right half of message blocks from 32 bits to 48 bits
-    private static int[] expansion = {32, 1, 2, 3, 4, 5, 4, 5, 6, 7, 8, 9, 8, 9, 10, 11, 12, 13, 12, 13, 14, 15, 16, 17, 16, 17, 18, 19, 20, 21, 20, 21, 22, 23, 24, 25, 24, 25, 26, 27, 28, 29, 28, 29, 30, 31, 32, 1};
+    private static final int[] EXPANSION = {32, 1, 2, 3, 4, 5, 4, 5, 6, 7, 8, 9, 8, 9, 10, 11, 12, 13, 12, 13, 14, 15, 16, 17, 16, 17, 18, 19, 20, 21, 20, 21, 22, 23, 24, 25, 24, 25, 26, 27, 28, 29, 28, 29, 30, 31, 32, 1};
 
     // The eight substitution boxes are defined below
-    private static int[][] s1 = {{14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7}, {0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8}, {4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0}, {15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13}};
+    private static final int[][] S1 = {{14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7}, {0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8}, {4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0}, {15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13}};
 
-    private static int[][] s2 = {{15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10}, {3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5}, {0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15}, {13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9}};
+    private static final int[][] S2 = {{15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10}, {3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5}, {0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15}, {13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9}};
 
-    private static int[][] s3 = {{10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8}, {13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1}, {13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7}, {1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12}};
+    private static final int[][] S3 = {{10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8}, {13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1}, {13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7}, {1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12}};
 
-    private static int[][] s4 = {{7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15}, {13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9}, {10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4}, {3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14}};
+    private static final int[][] S4 = {{7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15}, {13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9}, {10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4}, {3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14}};
 
-    private static int[][] s5 = {{2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9}, {14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6}, {4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14}, {11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3}};
+    private static final int[][] S5 = {{2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9}, {14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6}, {4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14}, {11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3}};
 
-    private static int[][] s6 = {{12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11}, {10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8}, {9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6}, {4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13}};
+    private static final int[][] S6 = {{12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11}, {10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8}, {9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6}, {4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13}};
 
-    private static int[][] s7 = {{4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1}, {13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6}, {1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2}, {6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12}};
+    private static final int[][] S7 = {{4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1}, {13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6}, {1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2}, {6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12}};
 
-    private static int[][] s8 = {{13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7}, {1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2}, {7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8}, {2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11}};
+    private static final int[][] S8 = {{13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7}, {1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2}, {7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8}, {2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11}};
 
-    private static int[][][] s = {s1, s2, s3, s4, s5, s6, s7, s8};
+    private static final int[][][] S = {S1, S2, S3, S4, S5, S6, S7, S8};
 
-    // Permutation table, used in the feistel function post s-box usage
-    static int[] permutation = {16, 7, 20, 21, 29, 12, 28, 17, 1, 15, 23, 26, 5, 18, 31, 10, 2, 8, 24, 14, 32, 27, 3, 9, 19, 13, 30, 6, 22, 11, 4, 25};
+    // Permutation table, used in the Feistel function post s-box usage
+    static final int[] PERMUTATION = {16, 7, 20, 21, 29, 12, 28, 17, 1, 15, 23, 26, 5, 18, 31, 10, 2, 8, 24, 14, 32, 27, 3, 9, 19, 13, 30, 6, 22, 11, 4, 25};
 
     // Table used for final inversion of the message box after 16 rounds of Feistel Function
-    static int[] IPinverse = {40, 8, 48, 16, 56, 24, 64, 32, 39, 7, 47, 15, 55, 23, 63, 31, 38, 6, 46, 14, 54, 22, 62, 30, 37, 5, 45, 13, 53, 21, 61, 29, 36, 4, 44, 12, 52, 20, 60, 28, 35, 3, 43, 11, 51, 19, 59, 27, 34, 2, 42, 10, 50, 18, 58, 26, 33, 1, 41, 9, 49, 17, 57, 25};
+    static final int[] IP_INVERSE = {40, 8, 48, 16, 56, 24, 64, 32, 39, 7, 47, 15, 55, 23, 63, 31, 38, 6, 46, 14, 54, 22, 62, 30, 37, 5, 45, 13, 53, 21, 61, 29, 36, 4, 44, 12, 52, 20, 60, 28, 35, 3, 43, 11, 51, 19, 59, 27, 34, 2, 42, 10, 50, 18, 58, 26, 33, 1, 41, 9, 49, 17, 57, 25};
 
     private String[] getSubkeys(String originalKey) {
-        StringBuilder permutedKey = new StringBuilder(); // Initial permutation of keys via PC1
-        int i, j;
+        StringBuilder permutedKey = new StringBuilder(); // Initial permutation of keys via pc1
+        int i;
+        int j;
         for (i = 0; i < 56; i++) {
             permutedKey.append(originalKey.charAt(PC1[i] - 1));
         }
-        String subKeys[] = new String[16];
+        String[] subKeys = new String[16];
         String initialPermutedKey = permutedKey.toString();
-        String C0 = initialPermutedKey.substring(0, 28), D0 = initialPermutedKey.substring(28);
+        String c0 = initialPermutedKey.substring(0, 28);
+        String d0 = initialPermutedKey.substring(28);
 
         // We will now operate on the left and right halves of the permutedKey
         for (i = 0; i < 16; i++) {
-            String Cn = C0.substring(KEY_SHIFTS[i]) + C0.substring(0, KEY_SHIFTS[i]);
-            String Dn = D0.substring(KEY_SHIFTS[i]) + D0.substring(0, KEY_SHIFTS[i]);
-            subKeys[i] = Cn + Dn;
-            C0 = Cn; // Re-assign the values to create running permutation
-            D0 = Dn;
+            String cN = c0.substring(KEY_SHIFTS[i]) + c0.substring(0, KEY_SHIFTS[i]);
+            String dN = d0.substring(KEY_SHIFTS[i]) + d0.substring(0, KEY_SHIFTS[i]);
+            subKeys[i] = cN + dN;
+            c0 = cN; // Re-assign the values to create running permutation
+            d0 = dN;
         }
 
-        // Let us shrink the keys to 48 bits (well, characters here) using PC2
+        // Let us shrink the keys to 48 bits (well, characters here) using pc2
         for (i = 0; i < 16; i++) {
             String key = subKeys[i];
             permutedKey.setLength(0);
@@ -104,8 +106,9 @@ public class DES {
         return subKeys;
     }
 
-    private String XOR(String a, String b) {
-        int i, l = a.length();
+    private String xOR(String a, String b) {
+        int i;
+        int l = a.length();
         StringBuilder xor = new StringBuilder();
         for (i = 0; i < l; i++) {
             int firstBit = a.charAt(i) - 48; // 48 is '0' in ascii
@@ -116,7 +119,8 @@ public class DES {
     }
 
     private String createPaddedString(String s, int desiredLength, char pad) {
-        int i, l = s.length();
+        int i;
+        int l = s.length();
         StringBuilder paddedString = new StringBuilder();
         int diff = desiredLength - l;
         for (i = 0; i < diff; i++) {
@@ -137,9 +141,9 @@ public class DES {
         int i;
         StringBuilder expandedKey = new StringBuilder();
         for (i = 0; i < 48; i++) {
-            expandedKey.append(messageBlock.charAt(expansion[i] - 1));
+            expandedKey.append(messageBlock.charAt(EXPANSION[i] - 1));
         }
-        String mixedKey = XOR(expandedKey.toString(), key);
+        String mixedKey = xOR(expandedKey.toString(), key);
         StringBuilder substitutedString = new StringBuilder();
 
         // Let us now use the s-boxes to transform each 6 bit (length here) block to 4 bits
@@ -147,45 +151,46 @@ public class DES {
             String block = mixedKey.substring(i, i + 6);
             int row = (block.charAt(0) - 48) * 2 + (block.charAt(5) - 48);
             int col = (block.charAt(1) - 48) * 8 + (block.charAt(2) - 48) * 4 + (block.charAt(3) - 48) * 2 + (block.charAt(4) - 48);
-            String substitutedBlock = pad(Integer.toBinaryString(s[i / 6][row][col]), 4);
+            String substitutedBlock = pad(Integer.toBinaryString(S[i / 6][row][col]), 4);
             substitutedString.append(substitutedBlock);
         }
 
         StringBuilder permutedString = new StringBuilder();
         for (i = 0; i < 32; i++) {
-            permutedString.append(substitutedString.charAt(permutation[i] - 1));
+            permutedString.append(substitutedString.charAt(PERMUTATION[i] - 1));
         }
 
         return permutedString.toString();
     }
 
-    private String encryptBlock(String message, String keys[]) {
+    private String encryptBlock(String message, String[] keys) {
         StringBuilder permutedMessage = new StringBuilder();
         int i;
         for (i = 0; i < 64; i++) {
             permutedMessage.append(message.charAt(IP[i] - 1));
         }
-        String L0 = permutedMessage.substring(0, 32), R0 = permutedMessage.substring(32);
+        String e0 = permutedMessage.substring(0, 32);
+        String f0 = permutedMessage.substring(32);
 
         // Iterate 16 times
         for (i = 0; i < 16; i++) {
-            String Ln = R0; // Previous Right block
-            String Rn = XOR(L0, feistel(R0, keys[i]));
-            L0 = Ln;
-            R0 = Rn;
+            String eN = f0; // Previous Right block
+            String fN = xOR(e0, feistel(f0, keys[i]));
+            e0 = eN;
+            f0 = fN;
         }
 
-        String combinedBlock = R0 + L0; // Reverse the 16th block
+        String combinedBlock = f0 + e0; // Reverse the 16th block
         permutedMessage.setLength(0);
         for (i = 0; i < 64; i++) {
-            permutedMessage.append(combinedBlock.charAt(IPinverse[i] - 1));
+            permutedMessage.append(combinedBlock.charAt(IP_INVERSE[i] - 1));
         }
         return permutedMessage.toString();
     }
 
     // To decode, we follow the same process as encoding, but with reversed keys
-    private String decryptBlock(String message, String keys[]) {
-        String reversedKeys[] = new String[keys.length];
+    private String decryptBlock(String message, String[] keys) {
+        String[] reversedKeys = new String[keys.length];
         for (int i = 0; i < keys.length; i++) {
             reversedKeys[i] = keys[keys.length - i - 1];
         }
@@ -198,7 +203,9 @@ public class DES {
      */
     public String encrypt(String message) {
         StringBuilder encryptedMessage = new StringBuilder();
-        int l = message.length(), i, j;
+        int l = message.length();
+        int i;
+        int j;
         if (l % 8 != 0) {
             int desiredLength = (l / 8 + 1) * 8;
             l = desiredLength;
@@ -223,14 +230,16 @@ public class DES {
      */
     public String decrypt(String message) {
         StringBuilder decryptedMessage = new StringBuilder();
-        int l = message.length(), i, j;
+        int l = message.length();
+        int i;
+        int j;
         if (l % 64 != 0) {
             throw new IllegalArgumentException("Encrypted message should be a multiple of 64 characters in length");
         }
         for (i = 0; i < l; i += 64) {
             String block = message.substring(i, i + 64);
-            String result = decryptBlock(block.toString(), subKeys);
-            byte res[] = new byte[8];
+            String result = decryptBlock(block, subKeys);
+            byte[] res = new byte[8];
             for (j = 0; j < 64; j += 8) {
                 res[j / 8] = (byte) Integer.parseInt(result.substring(j, j + 8), 2);
             }

src/main/java/com/thealgorithms/ciphers/HillCipher.java

@@ -11,7 +11,9 @@ import java.util.Scanner;
  * for encryption. The cipher key and plaintext/ciphertext are user inputs.
  * @author Ojasva Jain
  */
-public class HillCipher {
+public final class HillCipher {
+    private HillCipher() {
+    }
 
     static Scanner userInput = new Scanner(System.in);
 
@@ -33,7 +35,7 @@ public class HillCipher {
         validateDeterminant(keyMatrix, matrixSize);
 
         int[][] messageVector = new int[matrixSize][1];
-        String CipherText = "";
+        String cipherText = "";
         int[][] cipherMatrix = new int[matrixSize][1];
         int j = 0;
         while (j < message.length()) {
@@ -46,7 +48,8 @@ public class HillCipher {
                 System.out.println(messageVector[i][0]);
                 j++;
             }
-            int x, i;
+            int x;
+            int i;
             for (i = 0; i < matrixSize; i++) {
                 cipherMatrix[i][0] = 0;
 
@@ -57,10 +60,10 @@ public class HillCipher {
                 cipherMatrix[i][0] = cipherMatrix[i][0] % 26;
             }
             for (i = 0; i < matrixSize; i++) {
-                CipherText += (char) (cipherMatrix[i][0] + 65);
+                cipherText += (char) (cipherMatrix[i][0] + 65);
             }
         }
-        System.out.println("Ciphertext: " + CipherText);
+        System.out.println("Ciphertext: " + cipherText);
     }
 
     // Following function decrypts a message
@@ -81,7 +84,7 @@ public class HillCipher {
 
         // solving for the required plaintext message
         int[][] messageVector = new int[n][1];
-        String PlainText = "";
+        String plainText = "";
         int[][] plainMatrix = new int[n][1];
         int j = 0;
         while (j < message.length()) {
@@ -94,7 +97,8 @@ public class HillCipher {
                 System.out.println(messageVector[i][0]);
                 j++;
             }
-            int x, i;
+            int x;
+            int i;
             for (i = 0; i < n; i++) {
                 plainMatrix[i][0] = 0;
 
@@ -105,15 +109,18 @@ public class HillCipher {
                 plainMatrix[i][0] = plainMatrix[i][0] % 26;
             }
             for (i = 0; i < n; i++) {
-                PlainText += (char) (plainMatrix[i][0] + 65);
+                plainText += (char) (plainMatrix[i][0] + 65);
             }
         }
-        System.out.println("Plaintext: " + PlainText);
+        System.out.println("Plaintext: " + plainText);
     }
 
     // Determinant calculator
     public static int determinant(int[][] a, int n) {
-        int det = 0, sign = 1, p = 0, q = 0;
+        int det = 0;
+        int sign = 1;
+        int p = 0;
+        int q = 0;
 
         if (n == 1) {
             det = a[0][0];
@@ -142,7 +149,6 @@ public class HillCipher {
 
     // Function to implement Hill Cipher
     static void hillCipher(String message) {
-        message.toUpperCase();
         System.out.println("What do you want to process from the message?");
         System.out.println("Press 1: To Encrypt");
         System.out.println("Press 2: To Decrypt");

src/main/java/com/thealgorithms/ciphers/Polybius.java

@@ -13,9 +13,11 @@ package com.thealgorithms.ciphers;
  * @author Hikmet ÇAKIR
  * @since 08-07-2022+03:00
  */
-public class Polybius {
+public final class Polybius {
+    private Polybius() {
+    }
 
-    private static final char[][] key = {
+    private static final char[][] KEY = {
         //         0    1    2    3    4
         /* 0 */ {'A', 'B', 'C', 'D', 'E'},
         /* 1 */ {'F', 'G', 'H', 'I', 'J'},
@@ -26,9 +28,9 @@ public class Polybius {
 
     private static String findLocationByCharacter(final char character) {
         final StringBuilder location = new StringBuilder();
-        for (int i = 0; i < key.length; i++) {
-            for (int j = 0; j < key[i].length; j++) {
-                if (character == key[i][j]) {
+        for (int i = 0; i < KEY.length; i++) {
+            for (int j = 0; j < KEY[i].length; j++) {
+                if (character == KEY[i][j]) {
                     location.append(i).append(j);
                     break;
                 }
@@ -53,7 +55,7 @@ public class Polybius {
         for (int i = 0; i < chars.length; i += 2) {
             int pozitionX = Character.getNumericValue(chars[i]);
             int pozitionY = Character.getNumericValue(chars[i + 1]);
-            plaintext.append(key[pozitionX][pozitionY]);
+            plaintext.append(KEY[pozitionX][pozitionY]);
         }
         return plaintext.toString();
     }

src/main/java/com/thealgorithms/ciphers/ProductCipher.java

@@ -2,7 +2,9 @@ package com.thealgorithms.ciphers;
 
 import java.util.Scanner;
 
-class ProductCipher {
+final class ProductCipher {
+    private ProductCipher() {
+    }
 
     public static void main(String[] args) {
         try (Scanner sc = new Scanner(System.in)) {
@@ -24,8 +26,8 @@ class ProductCipher {
 
             // Transposition encryption
             String transpositionInput = substitutionOutput.toString();
-            int modulus;
-            if ((modulus = transpositionInput.length() % n) != 0) {
+            int modulus = transpositionInput.length() % n;
+            if (modulus != 0) {
                 modulus = n - modulus;
 
                 for (; modulus != 0; modulus--) {
@@ -66,7 +68,6 @@ class ProductCipher {
 
             System.out.println("Plaintext: ");
             System.out.println(plaintext);
-            sc.close();
         }
     }
 }

src/main/java/com/thealgorithms/ciphers/RSA.java

@@ -47,7 +47,7 @@ public class RSA {
     /**
      * Generate a new public and private key set.
      */
-    public synchronized void generateKeys(int bits) {
+    public final synchronized void generateKeys(int bits) {
         SecureRandom r = new SecureRandom();
         BigInteger p = new BigInteger(bits / 2, 100, r);
         BigInteger q = new BigInteger(bits / 2, 100, r);

src/main/java/com/thealgorithms/ciphers/a5/A5KeyStreamGenerator.java

@@ -31,7 +31,9 @@ public class A5KeyStreamGenerator extends CompositeLFSR {
     }
 
     public BitSet getNextKeyStream() {
-        for (int cycle = 1; cycle <= INITIAL_CLOCKING_CYCLES; ++cycle) this.clock();
+        for (int cycle = 1; cycle <= INITIAL_CLOCKING_CYCLES; ++cycle) {
+            this.clock();
+        }
 
         BitSet result = new BitSet(KEY_STREAM_LENGTH);
         for (int cycle = 1; cycle <= KEY_STREAM_LENGTH; ++cycle) {

src/main/java/com/thealgorithms/ciphers/a5/CompositeLFSR.java

@@ -19,17 +19,19 @@ public abstract class CompositeLFSR implements BaseLFSR {
         boolean result = false;
         for (var register : registers) {
             result ^= register.getLastBit();
-            if (register.getClockBit() == majorityBit) register.clock();
+            if (register.getClockBit() == majorityBit) {
+                register.clock();
+            }
         }
         return result;
     }
 
     private boolean getMajorityBit() {
         Map<Boolean, Integer> bitCount = new TreeMap<>();
-        bitCount.put(false, 0);
-        bitCount.put(true, 0);
+        bitCount.put(Boolean.FALSE, 0);
+        bitCount.put(Boolean.TRUE, 0);
 
         registers.forEach(lfsr -> bitCount.put(lfsr.getClockBit(), bitCount.get(lfsr.getClockBit()) + 1));
-        return bitCount.get(false) <= bitCount.get(true);
+        return bitCount.get(Boolean.FALSE) <= bitCount.get(Boolean.TRUE);
     }
 }

src/main/java/com/thealgorithms/ciphers/a5/Utils.java

@@ -7,7 +7,9 @@ package com.thealgorithms.ciphers.a5;
 
 import java.util.BitSet;
 
-public class Utils {
+public final class Utils {
+    private Utils() {
+    }
 
     public static boolean increment(BitSet bits, int size) {
         int i = size - 1;

src/main/java/com/thealgorithms/conversions/AffineConverter.java

@@ -0,0 +1,23 @@
+package com.thealgorithms.conversions;
+
+public final class AffineConverter {
+    private final double slope;
+    private final double intercept;
+    public AffineConverter(final double inSlope, final double inIntercept) {
+        slope = inSlope;
+        intercept = inIntercept;
+    }
+
+    public double convert(final double inValue) {
+        return slope * inValue + intercept;
+    }
+
+    public AffineConverter invert() {
+        assert slope != 0.0;
+        return new AffineConverter(1.0 / slope, -intercept / slope);
+    }
+
+    public AffineConverter compose(final AffineConverter other) {
+        return new AffineConverter(slope * other.slope, slope * other.intercept + intercept);
+    }
+}

src/main/java/com/thealgorithms/conversions/AnyBaseToAnyBase.java

@@ -13,7 +13,9 @@ import java.util.Scanner;
  * @author Michael Rolland
  * @version 2017.10.10
  */
-public class AnyBaseToAnyBase {
+public final class AnyBaseToAnyBase {
+    private AnyBaseToAnyBase() {
+    }
 
     /**
      * Smallest and largest base you want to accept as valid input
@@ -25,7 +27,8 @@ public class AnyBaseToAnyBase {
     public static void main(String[] args) {
         Scanner in = new Scanner(System.in);
         String n;
-        int b1, b2;
+        int b1;
+        int b2;
         while (true) {
             try {
                 System.out.print("Enter number: ");
@@ -130,7 +133,8 @@ public class AnyBaseToAnyBase {
         // Declare variables: decimal value of n,
         // character of base b1, character of base b2,
         // and the string that will be returned.
-        int decimalValue = 0, charB2;
+        int decimalValue = 0;
+        int charB2;
         char charB1;
         String output = "";
         // Go through every character of n

src/main/java/com/thealgorithms/conversions/AnyBaseToDecimal.java

@@ -3,52 +3,50 @@ package com.thealgorithms.conversions;
 /**
  * @author Varun Upadhyay (<a href="https://github.com/varunu28">...</a>)
  */
-// Driver program
-public class AnyBaseToDecimal {
+public final class AnyBaseToDecimal {
+    private static final int CHAR_OFFSET_FOR_DIGIT = '0';
+    private static final int CHAR_OFFSET_FOR_UPPERCASE = 'A' - 10;
 
-    public static void main(String[] args) {
-        assert convertToDecimal("1010", 2) == Integer.valueOf("1010", 2);
-        assert convertToDecimal("777", 8) == Integer.valueOf("777", 8);
-        assert convertToDecimal("999", 10) == Integer.valueOf("999", 10);
-        assert convertToDecimal("ABCDEF", 16) == Integer.valueOf("ABCDEF", 16);
-        assert convertToDecimal("XYZ", 36) == Integer.valueOf("XYZ", 36);
+    private AnyBaseToDecimal() {
     }
 
     /**
-     * Convert any radix to decimal number
+     * Convert any radix to a decimal number.
      *
-     * @param s the string to be convert
-     * @param radix the radix
-     * @return decimal of bits
-     * @throws NumberFormatException if {@code bits} or {@code radix} is invalid
+     * @param input the string to be converted
+     * @param radix the radix (base) of the input string
+     * @return the decimal equivalent of the input string
+     * @throws NumberFormatException if the input string or radix is invalid
      */
-    public static int convertToDecimal(String s, int radix) {
-        int num = 0;
-        int pow = 1;
+    public static int convertToDecimal(String input, int radix) {
+        int result = 0;
+        int power = 1;
 
-        for (int i = s.length() - 1; i >= 0; i--) {
-            int digit = valOfChar(s.charAt(i));
+        for (int i = input.length() - 1; i >= 0; i--) {
+            int digit = valOfChar(input.charAt(i));
             if (digit >= radix) {
-                throw new NumberFormatException("For input string " + s);
+                throw new NumberFormatException("For input string: " + input);
             }
-            num += valOfChar(s.charAt(i)) * pow;
-            pow *= radix;
+            result += digit * power;
+            power *= radix;
         }
-        return num;
+        return result;
     }
 
     /**
-     * Convert character to integer
+     * Convert a character to its integer value.
      *
-     * @param c the character
-     * @return represented digit of given character
-     * @throws NumberFormatException if {@code ch} is not UpperCase or Digit
-     * character.
+     * @param character the character to be converted
+     * @return the integer value represented by the character
+     * @throws NumberFormatException if the character is not an uppercase letter or a digit
      */
-    public static int valOfChar(char c) {
-        if (!(Character.isUpperCase(c) || Character.isDigit(c))) {
-            throw new NumberFormatException("invalid character :" + c);
+    private static int valOfChar(char character) {
+        if (Character.isDigit(character)) {
+            return character - CHAR_OFFSET_FOR_DIGIT;
+        } else if (Character.isUpperCase(character)) {
+            return character - CHAR_OFFSET_FOR_UPPERCASE;
+        } else {
+            throw new NumberFormatException("invalid character:" + character);
         }
-        return Character.isDigit(c) ? c - '0' : c - 'A' + 10;
     }
 }

src/main/java/com/thealgorithms/conversions/AnytoAny.java

@@ -6,14 +6,18 @@ import java.util.Scanner;
 // number.
 // sn ,sb,db ---> ()dn  .   this is what we have to do    .
 
-public class AnytoAny {
+public final class AnytoAny {
+    private AnytoAny() {
+    }
 
     public static void main(String[] args) {
         Scanner scn = new Scanner(System.in);
         int sn = scn.nextInt();
         int sb = scn.nextInt();
         int db = scn.nextInt();
-        int m = 1, dec = 0, dn = 0;
+        int m = 1;
+        int dec = 0;
+        int dn = 0;
         while (sn != 0) {
             dec = dec + (sn % 10) * m;
             m *= sb;

src/main/java/com/thealgorithms/conversions/BinaryToDecimal.java

@@ -1,32 +1,33 @@
 package com.thealgorithms.conversions;
 
-import java.util.Scanner;
-
 /**
  * This class converts a Binary number to a Decimal number
  */
-class BinaryToDecimal {
+final class BinaryToDecimal {
+    private static final int BINARY_BASE = 2;
 
-    public static long binaryToDecimal(long binNum) {
-        long binCopy, d, s = 0, power = 0;
-        binCopy = binNum;
-        while (binCopy != 0) {
-            d = binCopy % 10;
-            s += d * (long) Math.pow(2, power++);
-            binCopy /= 10;
-        }
-        return s;
+    private BinaryToDecimal() {
     }
 
     /**
-     * Main Method
+     * Converts a binary number to its decimal equivalent.
      *
-     * @param args Command line arguments
+     * @param binaryNumber The binary number to convert.
+     * @return The decimal equivalent of the binary number.
+     * @throws IllegalArgumentException If the binary number contains digits other than 0 and 1.
      */
-    public static void main(String[] args) {
-        Scanner sc = new Scanner(System.in);
-        System.out.print("Binary number: ");
-        System.out.println("Decimal equivalent:" + binaryToDecimal(sc.nextLong()));
-        sc.close();
+    public static long binaryToDecimal(long binaryNumber) {
+        long decimalValue = 0;
+        long power = 0;
+
+        while (binaryNumber != 0) {
+            long digit = binaryNumber % 10;
+            if (digit > 1) {
+                throw new IllegalArgumentException("Incorrect binary digit: " + digit);
+            }
+            decimalValue += (long) (digit * Math.pow(BINARY_BASE, power++));
+            binaryNumber /= 10;
+        }
+        return decimalValue;
     }
 }

src/main/java/com/thealgorithms/conversions/BinaryToHexadecimal.java

@@ -1,57 +1,63 @@
 package com.thealgorithms.conversions;
 
-import java.util.*;
+import java.util.HashMap;
+import java.util.Map;
 
 /**
  * Converts any Binary Number to a Hexadecimal Number
  *
  * @author Nishita Aggarwal
  */
-public class BinaryToHexadecimal {
+public final class BinaryToHexadecimal {
+    private static final int BITS_IN_HEX_DIGIT = 4;
+    private static final int BASE_BINARY = 2;
+    private static final int BASE_DECIMAL = 10;
+    private static final int HEX_START_DECIMAL = 10;
+    private static final int HEX_END_DECIMAL = 15;
 
-    /**
-     * This method converts a binary number to a hexadecimal number.
-     *
-     * @param binary The binary number
-     * @return The hexadecimal number
-     */
-    static String binToHex(int binary) {
-        // hm to store hexadecimal codes for binary numbers within the range: 0000 to 1111 i.e. for
-        // decimal numbers 0 to 15
-        HashMap<Integer, String> hm = new HashMap<>();
-        // String to store hexadecimal code
-        String hex = "";
-        int i;
-        for (i = 0; i < 10; i++) {
-            hm.put(i, String.valueOf(i));
-        }
-        for (i = 10; i < 16; i++) {
-            hm.put(i, String.valueOf((char) ('A' + i - 10)));
-        }
-        int currbit;
-        while (binary != 0) {
-            int code4 = 0; // to store decimal equivalent of number formed by 4 decimal digits
-            for (i = 0; i < 4; i++) {
-                currbit = binary % 10;
-                binary = binary / 10;
-                code4 += currbit * (int) Math.pow(2, i);
-            }
-            hex = hm.get(code4) + hex;
-        }
-        return hex;
+    private BinaryToHexadecimal() {
     }
 
     /**
-     * Main method
+     * Converts a binary number to a hexadecimal number.
      *
-     * @param args Command line arguments
+     * @param binary The binary number to convert.
+     * @return The hexadecimal representation of the binary number.
+     * @throws IllegalArgumentException If the binary number contains digits other than 0 and 1.
      */
-    public static void main(String[] args) {
-        Scanner sc = new Scanner(System.in);
-        System.out.println("Enter binary number:");
-        int binary = sc.nextInt();
-        String hex = binToHex(binary);
-        System.out.println("Hexadecimal Code:" + hex);
-        sc.close();
+    public static String binToHex(int binary) {
+        Map<Integer, String> hexMap = initializeHexMap();
+        StringBuilder hex = new StringBuilder();
+
+        while (binary != 0) {
+            int decimalValue = 0;
+            for (int i = 0; i < BITS_IN_HEX_DIGIT; i++) {
+                int currentBit = binary % BASE_DECIMAL;
+                if (currentBit > 1) {
+                    throw new IllegalArgumentException("Incorrect binary digit: " + currentBit);
+                }
+                binary /= BASE_DECIMAL;
+                decimalValue += (int) (currentBit * Math.pow(BASE_BINARY, i));
+            }
+            hex.insert(0, hexMap.get(decimalValue));
+        }
+
+        return !hex.isEmpty() ? hex.toString() : "0";
+    }
+
+    /**
+     * Initializes the hexadecimal map with decimal to hexadecimal mappings.
+     *
+     * @return The initialized map containing mappings from decimal numbers to hexadecimal digits.
+     */
+    private static Map<Integer, String> initializeHexMap() {
+        Map<Integer, String> hexMap = new HashMap<>();
+        for (int i = 0; i < BASE_DECIMAL; i++) {
+            hexMap.put(i, String.valueOf(i));
+        }
+        for (int i = HEX_START_DECIMAL; i <= HEX_END_DECIMAL; i++) {
+            hexMap.put(i, String.valueOf((char) ('A' + i - HEX_START_DECIMAL)));
+        }
+        return hexMap;
     }
 }

src/main/java/com/thealgorithms/conversions/BinaryToOctal.java

@@ -1,25 +1,11 @@
 package com.thealgorithms.conversions;
 
-import java.util.Scanner;
+public final class BinaryToOctal {
+    private static final int BITS_PER_OCTAL_DIGIT = 3;
+    private static final int BINARY_BASE = 2;
+    private static final int DECIMAL_BASE = 10;
 
-/**
- * Converts any Binary number to an Octal Number
- *
- * @author Zachary Jones
- */
-public class BinaryToOctal {
-
-    /**
-     * Main method
-     *
-     * @param args Command line arguments
-     */
-    public static void main(String[] args) {
-        Scanner sc = new Scanner(System.in);
-        System.out.println("Input the binary number: ");
-        int b = sc.nextInt();
-        System.out.println("Octal equivalent: " + convertBinaryToOctal(b));
-        sc.close();
+    private BinaryToOctal() {
     }
 
     /**
@@ -27,21 +13,33 @@ public class BinaryToOctal {
      *
      * @param binary The binary number
      * @return The octal number
+     * @throws IllegalArgumentException if the input is not a valid binary number
      */
     public static String convertBinaryToOctal(int binary) {
-        String octal = "";
-        int currBit = 0, j = 1;
-        while (binary != 0) {
-            int code3 = 0;
-            for (int i = 0; i < 3; i++) {
-                currBit = binary % 10;
-                binary = binary / 10;
-                code3 += currBit * j;
-                j *= 2;
-            }
-            octal = code3 + octal;
-            j = 1;
+        if (binary == 0) {
+            return "0";
         }
-        return octal;
+
+        if (!String.valueOf(binary).matches("[01]+")) {
+            throw new IllegalArgumentException("Input is not a valid binary number.");
+        }
+
+        StringBuilder octal = new StringBuilder();
+        int currentBit;
+        int bitValueMultiplier = 1;
+
+        while (binary != 0) {
+            int octalDigit = 0;
+            for (int i = 0; i < BITS_PER_OCTAL_DIGIT && binary != 0; i++) {
+                currentBit = binary % DECIMAL_BASE;
+                binary /= DECIMAL_BASE;
+                octalDigit += currentBit * bitValueMultiplier;
+                bitValueMultiplier *= BINARY_BASE;
+            }
+            octal.insert(0, octalDigit);
+            bitValueMultiplier = 1; // Reset multiplier for the next group
+        }
+
+        return octal.toString();
     }
 }

src/main/java/com/thealgorithms/conversions/DecimalToAnyBase.java

@@ -1,67 +1,69 @@
 package com.thealgorithms.conversions;
 
-import java.io.BufferedReader;
-import java.io.InputStreamReader;
 import java.util.ArrayList;
+import java.util.List;
 
 /**
+ *  Class that provides methods to convert a decimal number to a string representation
+ *  in any specified base between 2 and 36.
+ *
  * @author Varun Upadhyay (<a href="https://github.com/varunu28">...</a>)
  */
-// Driver Program
-public class DecimalToAnyBase {
+public final class DecimalToAnyBase {
+    private static final int MIN_BASE = 2;
+    private static final int MAX_BASE = 36;
+    private static final char ZERO_CHAR = '0';
+    private static final char A_CHAR = 'A';
+    private static final int DIGIT_OFFSET = 10;
 
-    public static void main(String[] args) throws Exception {
-        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
-        System.out.println("Enter the decimal input below: ");
-        int decInput = Integer.parseInt(br.readLine());
-        System.out.println();
-
-        System.out.println("Enter the base below: ");
-        int base = Integer.parseInt(br.readLine());
-        System.out.println();
-
-        System.out.println("Decimal Input"
-            + " is: " + decInput);
-        System.out.println("Value of " + decInput + " in base " + base + " is: " + convertToAnyBase(decInput, base));
-
-        br.close();
+    private DecimalToAnyBase() {
     }
 
     /**
-     * This method produces a String value of any given input decimal in any
-     * base
+     * Converts a decimal number to a string representation in the specified base.
+     * For example, converting the decimal number 10 to base 2 would return "1010".
      *
-     * @param inp Decimal of which we need the value in base in String format
-     * @return string format of the converted value in the given base
+     * @param decimal the decimal number to convert
+     * @param base    the base to convert to (must be between {@value #MIN_BASE} and {@value #MAX_BASE})
+     * @return the string representation of the number in the specified base
+     * @throws IllegalArgumentException if the base is out of the supported range
      */
-    public static String convertToAnyBase(int inp, int base) {
-        ArrayList<Character> charArr = new ArrayList<>();
-
-        while (inp > 0) {
-            charArr.add(reVal(inp % base));
-            inp /= base;
+    public static String convertToAnyBase(int decimal, int base) {
+        if (base < MIN_BASE || base > MAX_BASE) {
+            throw new IllegalArgumentException("Base must be between " + MIN_BASE + " and " + MAX_BASE);
         }
 
-        StringBuilder str = new StringBuilder(charArr.size());
-
-        for (Character ch : charArr) {
-            str.append(ch);
+        if (decimal == 0) {
+            return String.valueOf(ZERO_CHAR);
         }
 
-        return str.reverse().toString();
+        List<Character> digits = new ArrayList<>();
+        while (decimal > 0) {
+            digits.add(convertToChar(decimal % base));
+            decimal /= base;
+        }
+
+        StringBuilder result = new StringBuilder(digits.size());
+        for (int i = digits.size() - 1; i >= 0; i--) {
+            result.append(digits.get(i));
+        }
+
+        return result.toString();
     }
 
     /**
-     * This method produces character value of the input integer and returns it
+     * Converts an integer value to its corresponding character in the specified base.
+     * This method is used to convert values from 0 to 35 into their appropriate character representation.
+     * For example, 0-9 are represented as '0'-'9', and 10-35 are represented as 'A'-'Z'.
      *
-     * @param num integer of which we need the character value of
-     * @return character value of input integer
+     * @param value the integer value to convert (should be less than the base value)
+     * @return the character representing the value in the specified base
      */
-    public static char reVal(int num) {
-        if (num >= 0 && num <= 9) {
-            return (char) (num + '0');
+    private static char convertToChar(int value) {
+        if (value >= 0 && value <= 9) {
+            return (char) (ZERO_CHAR + value);
         } else {
-            return (char) (num - 10 + 'A');
+            return (char) (A_CHAR + value - DIGIT_OFFSET);
         }
     }
 }

src/main/java/com/thealgorithms/conversions/DecimalToBinary.java

@@ -1,55 +1,49 @@
 package com.thealgorithms.conversions;
 
-import java.util.Scanner;
-
 /**
- * This class converts a Decimal number to a Binary number
+ * This class provides methods to convert a decimal number to a binary number.
  */
-class DecimalToBinary {
+final class DecimalToBinary {
+    private static final int BINARY_BASE = 2;
+    private static final int DECIMAL_MULTIPLIER = 10;
 
-    /**
-     * Main Method
-     *
-     * @param args Command Line Arguments
-     */
-    public static void main(String[] args) {
-        conventionalConversion();
-        bitwiseConversion();
+    private DecimalToBinary() {
     }
 
     /**
-     * This method converts a decimal number to a binary number using a
-     * conventional algorithm.
+     * Converts a decimal number to a binary number using a conventional algorithm.
+     * @param decimalNumber the decimal number to convert
+     * @return the binary representation of the decimal number
      */
-    public static void conventionalConversion() {
-        int n, b = 0, c = 0, d;
-        Scanner input = new Scanner(System.in);
-        System.out.printf("Conventional conversion.%n Enter the decimal number: ");
-        n = input.nextInt();
-        while (n != 0) {
-            d = n % 2;
-            b = b + d * (int) Math.pow(10, c++);
-            n /= 2;
-        } // converting decimal to binary
-        System.out.println("\tBinary number: " + b);
-        input.close();
-    }
+    public static int convertUsingConventionalAlgorithm(int decimalNumber) {
+        int binaryNumber = 0;
+        int position = 1;
 
-    /**
-     * This method converts a decimal number to a binary number using a bitwise
-     * algorithm
-     */
-    public static void bitwiseConversion() {
-        int n, b = 0, c = 0, d;
-        Scanner input = new Scanner(System.in);
-        System.out.printf("Bitwise conversion.%n Enter the decimal number: ");
-        n = input.nextInt();
-        while (n != 0) {
-            d = (n & 1);
-            b += d * (int) Math.pow(10, c++);
-            n >>= 1;
+        while (decimalNumber > 0) {
+            int remainder = decimalNumber % BINARY_BASE;
+            binaryNumber += remainder * position;
+            position *= DECIMAL_MULTIPLIER;
+            decimalNumber /= BINARY_BASE;
         }
-        System.out.println("\tBinary number: " + b);
-        input.close();
+
+        return binaryNumber;
+    }
+
+    /**
+     * Converts a decimal number to a binary number using a bitwise algorithm.
+     * @param decimalNumber the decimal number to convert
+     * @return the binary representation of the decimal number
+     */
+    public static int convertUsingBitwiseAlgorithm(int decimalNumber) {
+        int binaryNumber = 0;
+        int position = 1;
+
+        while (decimalNumber > 0) {
+            int leastSignificantBit = decimalNumber & 1;
+            binaryNumber += leastSignificantBit * position;
+            position *= DECIMAL_MULTIPLIER;
+            decimalNumber >>= 1;
+        }
+        return binaryNumber;
     }
 }

src/main/java/com/thealgorithms/conversions/DecimalToHexaDecimal.java

@@ -1,49 +0,0 @@
-package com.thealgorithms.conversions;
-
-// hex = [0 - 9] -> [A - F]
-class DecimalToHexaDecimal {
-
-    private static final int sizeOfIntInHalfBytes = 8;
-    private static final int numberOfBitsInAHalfByte = 4;
-    private static final int halfByte = 0x0F;
-    private static final char[] hexDigits = {
-        '0',
-        '1',
-        '2',
-        '3',
-        '4',
-        '5',
-        '6',
-        '7',
-        '8',
-        '9',
-        'A',
-        'B',
-        'C',
-        'D',
-        'E',
-        'F',
-    };
-
-    // Returns the hex value of the dec entered in the parameter.
-    public static String decToHex(int dec) {
-        StringBuilder hexBuilder = new StringBuilder(sizeOfIntInHalfBytes);
-        hexBuilder.setLength(sizeOfIntInHalfBytes);
-        for (int i = sizeOfIntInHalfBytes - 1; i >= 0; --i) {
-            int j = dec & halfByte;
-            hexBuilder.setCharAt(i, hexDigits[j]);
-            dec >>= numberOfBitsInAHalfByte;
-        }
-        return hexBuilder.toString().toLowerCase();
-    }
-
-    // Test above function.
-    public static void main(String[] args) {
-        System.out.println("Test...");
-        int dec = 305445566;
-        String libraryDecToHex = Integer.toHexString(dec);
-        String decToHex = decToHex(dec);
-        System.out.println("Result from the library : " + libraryDecToHex);
-        System.out.println("Result decToHex method : " + decToHex);
-    }
-}

src/main/java/com/thealgorithms/conversions/DecimalToHexadecimal.java

@@ -0,0 +1,42 @@
+package com.thealgorithms.conversions;
+
+/**
+ * This class provides a method to convert a decimal number to a hexadecimal string.
+ */
+final class DecimalToHexadecimal {
+    private static final int SIZE_OF_INT_IN_HALF_BYTES = 8;
+    private static final int NUMBER_OF_BITS_IN_HALF_BYTE = 4;
+    private static final int HALF_BYTE_MASK = 0x0F;
+    private static final char[] HEX_DIGITS = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
+
+    private DecimalToHexadecimal() {
+    }
+
+    /**
+     * Converts a decimal number to a hexadecimal string.
+     * @param decimal the decimal number to convert
+     * @return the hexadecimal representation of the decimal number
+     */
+    public static String decToHex(int decimal) {
+        StringBuilder hexBuilder = new StringBuilder(SIZE_OF_INT_IN_HALF_BYTES);
+        for (int i = SIZE_OF_INT_IN_HALF_BYTES - 1; i >= 0; --i) {
+            int currentHalfByte = decimal & HALF_BYTE_MASK;
+            hexBuilder.insert(0, HEX_DIGITS[currentHalfByte]);
+            decimal >>= NUMBER_OF_BITS_IN_HALF_BYTE;
+        }
+        return removeLeadingZeros(hexBuilder.toString().toLowerCase());
+    }
+
+    private static String removeLeadingZeros(String str) {
+        if (str == null || str.isEmpty()) {
+            return str;
+        }
+
+        int i = 0;
+        while (i < str.length() && str.charAt(i) == '0') {
+            i++;
+        }
+
+        return i == str.length() ? "0" : str.substring(i);
+    }
+}

src/main/java/com/thealgorithms/conversions/DecimalToOctal.java

@@ -1,32 +1,38 @@
 package com.thealgorithms.conversions;
 
-import java.util.Scanner;
-
 /**
  * This class converts Decimal numbers to Octal Numbers
  */
-public class DecimalToOctal {
+public final class DecimalToOctal {
+    private static final int OCTAL_BASE = 8;
+    private static final int INITIAL_OCTAL_VALUE = 0;
+    private static final int INITIAL_PLACE_VALUE = 1;
+
+    private DecimalToOctal() {
+    }
 
     /**
-     * Main Method
+     * Converts a decimal number to its octal equivalent.
      *
-     * @param args Command line Arguments
+     * @param decimal The decimal number to convert.
+     * @return The octal equivalent as an integer.
+     * @throws IllegalArgumentException if the decimal number is negative.
      */
-
-    // enter in a decimal value to get Octal output
-    public static void main(String[] args) {
-        Scanner sc = new Scanner(System.in);
-        int n, k, d, s = 0, c = 0;
-        System.out.print("Decimal number: ");
-        n = sc.nextInt();
-        k = n;
-        while (k != 0) {
-            d = k % 8;
-            s += d * (int) Math.pow(10, c++);
-            k /= 8;
+    public static int convertToOctal(int decimal) {
+        if (decimal < 0) {
+            throw new IllegalArgumentException("Decimal number cannot be negative.");
         }
 
-        System.out.println("Octal equivalent:" + s);
-        sc.close();
+        int octal = INITIAL_OCTAL_VALUE;
+        int placeValue = INITIAL_PLACE_VALUE;
+
+        while (decimal != 0) {
+            int remainder = decimal % OCTAL_BASE;
+            octal += remainder * placeValue;
+            decimal /= OCTAL_BASE;
+            placeValue *= 10;
+        }
+
+        return octal;
     }
 }

src/main/java/com/thealgorithms/conversions/HexToOct.java

@@ -1,72 +1,62 @@
 package com.thealgorithms.conversions;
 
-import java.util.Scanner;
-
 /**
  * Converts any Hexadecimal Number to Octal
  *
  * @author Tanmay Joshi
  */
-public class HexToOct {
-
-    /**
-     * This method converts a Hexadecimal number to a decimal number
-     *
-     * @param s The Hexadecimal Number
-     * @return The Decimal number
-     */
-    public static int hex2decimal(String s) {
-        String str = "0123456789ABCDEF";
-        s = s.toUpperCase();
-        int val = 0;
-        for (int i = 0; i < s.length(); i++) {
-            char a = s.charAt(i);
-            int n = str.indexOf(a);
-            val = 16 * val + n;
-        }
-        return val;
+public final class HexToOct {
+    private HexToOct() {
     }
 
     /**
-     * This method converts a Decimal number to a octal number
+     * Converts a Hexadecimal number to a Decimal number.
      *
-     * @param q The Decimal Number
-     * @return The Octal number
+     * @param hex The Hexadecimal number as a String.
+     * @return The Decimal equivalent as an integer.
      */
-    public static int decimal2octal(int q) {
-        int now;
-        int i = 1;
-        int octnum = 0;
-        while (q > 0) {
-            now = q % 8;
-            octnum = (now * (int) (Math.pow(10, i))) + octnum;
-            q /= 8;
-            i++;
+    public static int hexToDecimal(String hex) {
+        String hexDigits = "0123456789ABCDEF";
+        hex = hex.toUpperCase();
+        int decimalValue = 0;
+
+        for (int i = 0; i < hex.length(); i++) {
+            char hexChar = hex.charAt(i);
+            int digitValue = hexDigits.indexOf(hexChar);
+            decimalValue = 16 * decimalValue + digitValue;
         }
-        octnum /= 10;
-        return octnum;
+
+        return decimalValue;
     }
 
     /**
-     * Main method that gets the hex input from user and converts it into octal.
+     * Converts a Decimal number to an Octal number.
      *
-     * @param args arguments
+     * @param decimal The Decimal number as an integer.
+     * @return The Octal equivalent as an integer.
      */
-    public static void main(String[] args) {
-        String hexadecnum;
-        int decnum, octalnum;
-        Scanner scan = new Scanner(System.in);
+    public static int decimalToOctal(int decimal) {
+        int octalValue = 0;
+        int placeValue = 1;
 
-        System.out.print("Enter Hexadecimal Number : ");
-        hexadecnum = scan.nextLine();
+        while (decimal > 0) {
+            int remainder = decimal % 8;
+            octalValue += remainder * placeValue;
+            decimal /= 8;
+            placeValue *= 10;
+        }
 
-        // first convert hexadecimal to decimal
-        decnum = hex2decimal(hexadecnum); // Pass the string to the hex2decimal function and get the decimal form in
-        // variable decnum
+        return octalValue;
+    }
 
-        // convert decimal to octal
-        octalnum = decimal2octal(decnum);
-        System.out.println("Number in octal: " + octalnum);
-        scan.close();
+    /**
+     * Converts a Hexadecimal number to an Octal number.
+     *
+     * @param hex The Hexadecimal number as a String.
+     * @return The Octal equivalent as an integer.
+     */
+    public static int hexToOctal(String hex) {
+        int decimalValue = hexToDecimal(hex);
+        return decimalToOctal(decimalValue);
     }
 }

src/main/java/com/thealgorithms/conversions/HexaDecimalToBinary.java

@@ -2,9 +2,6 @@ package com.thealgorithms.conversions;
 
 // Hex [0-9],[A-F] -> Binary [0,1]
 public class HexaDecimalToBinary {
-
-    private final int LONG_BITS = 8;
-
     public String convert(String numHex) {
         // String a HexaDecimal:
         int conHex = Integer.parseInt(numHex, 16);
@@ -15,7 +12,8 @@ public class HexaDecimalToBinary {
     }
 
     public String completeDigits(String binNum) {
-        for (int i = binNum.length(); i < LONG_BITS; i++) {
+        final int longBits = 8;
+        for (int i = binNum.length(); i < longBits; i++) {
             binNum = "0" + binNum;
         }
         return binNum;

src/main/java/com/thealgorithms/conversions/HexaDecimalToDecimal.java

@@ -2,7 +2,9 @@ package com.thealgorithms.conversions;
 
 import java.util.Scanner;
 
-public class HexaDecimalToDecimal {
+public final class HexaDecimalToDecimal {
+    private HexaDecimalToDecimal() {
+    }
 
     // convert hexadecimal to decimal
     public static int getHexaToDec(String hex) {
@@ -18,20 +20,20 @@ public class HexaDecimalToDecimal {
 
     // Main method gets the hexadecimal input from user and converts it into Decimal output.
     public static void main(String[] args) {
-        String hexa_Input;
-        int dec_output;
+        String hexaInput;
+        int decOutput;
         Scanner scan = new Scanner(System.in);
 
         System.out.print("Enter Hexadecimal Number : ");
-        hexa_Input = scan.nextLine();
+        hexaInput = scan.nextLine();
 
         // convert hexadecimal to decimal
-        dec_output = getHexaToDec(hexa_Input);
+        decOutput = getHexaToDec(hexaInput);
         /*
     Pass the string to the getHexaToDec function
-    and it returns the decimal form in the variable dec_output.
+    and it returns the decimal form in the variable decOutput.
          */
-        System.out.println("Number in Decimal: " + dec_output);
+        System.out.println("Number in Decimal: " + decOutput);
         scan.close();
     }
 }

src/main/java/com/thealgorithms/conversions/IntegerToRoman.java

@@ -7,9 +7,11 @@ package com.thealgorithms.conversions;
  * ('I', 1); ('IV',4); ('V', 5); ('IX',9); ('X', 10); ('XL',40); ('L', 50);
  * ('XC',90); ('C', 100); ('D', 500); ('M', 1000);
  */
-public class IntegerToRoman {
+public final class IntegerToRoman {
+    private IntegerToRoman() {
+    }
 
-    private static final int[] allArabianRomanNumbers = new int[] {
+    private static final int[] ALL_ROMAN_NUMBERS_IN_ARABIC = new int[] {
         1000,
         900,
         500,
@@ -24,7 +26,7 @@ public class IntegerToRoman {
         4,
         1,
     };
-    private static final String[] allRomanNumbers = new String[] {
+    private static final String[] ALL_ROMAN_NUMBERS = new String[] {
         "M",
         "CM",
         "D",
@@ -48,13 +50,13 @@ public class IntegerToRoman {
 
         StringBuilder builder = new StringBuilder();
 
-        for (int a = 0; a < allArabianRomanNumbers.length; a++) {
-            int times = num / allArabianRomanNumbers[a];
+        for (int a = 0; a < ALL_ROMAN_NUMBERS_IN_ARABIC.length; a++) {
+            int times = num / ALL_ROMAN_NUMBERS_IN_ARABIC[a];
             for (int b = 0; b < times; b++) {
-                builder.append(allRomanNumbers[a]);
+                builder.append(ALL_ROMAN_NUMBERS[a]);
             }
 
-            num -= times * allArabianRomanNumbers[a];
+            num -= times * ALL_ROMAN_NUMBERS_IN_ARABIC[a];
         }
 
         return builder.toString();

src/main/java/com/thealgorithms/conversions/OctalToBinary.java

@@ -6,7 +6,9 @@ package com.thealgorithms.conversions;
  * @author Bama Charan Chhandogi
  */
 
-public class OctalToBinary {
+public final class OctalToBinary {
+    private OctalToBinary() {
+    }
     public static long convertOctalToBinary(int octalNumber) {
         long binaryNumber = 0;
         int digitPosition = 1;

src/main/java/com/thealgorithms/conversions/OctalToDecimal.java

@@ -1,45 +1,42 @@
 package com.thealgorithms.conversions;
 
-import java.util.Scanner;
-
 /**
- * Converts any Octal Number to a Decimal Number
+ * Class for converting an octal number to a decimal number. Octal numbers are based on 8, using digits from 0 to 7.
  *
- * @author Zachary Jones
  */
-public class OctalToDecimal {
+public final class OctalToDecimal {
+    private static final int OCTAL_BASE = 8;
 
-    /**
-     * Main method
-     *
-     * @param args Command line arguments
-     */
-    public static void main(String[] args) {
-        Scanner sc = new Scanner(System.in);
-        System.out.print("Octal Input: ");
-        String inputOctal = sc.nextLine();
-        int result = convertOctalToDecimal(inputOctal);
-        if (result != -1) {
-            System.out.println("Result convertOctalToDecimal : " + result);
-        }
-        sc.close();
+    private OctalToDecimal() {
     }
 
     /**
-     * This method converts an octal number to a decimal number.
+     * Converts a given octal number (as a string) to its decimal representation.
+     * If the input is not a valid octal number (i.e., contains characters other than 0-7),
+     * the method throws an IllegalArgumentException.
      *
-     * @param inputOctal The octal number
-     * @return The decimal number
+     * @param inputOctal The octal number as a string
+     * @return The decimal equivalent of the octal number
+     * @throws IllegalArgumentException if the input is not a valid octal number
      */
     public static int convertOctalToDecimal(String inputOctal) {
-        try {
-            // Actual conversion of Octal to Decimal:
-            return Integer.parseInt(inputOctal, 8);
-        } catch (NumberFormatException ne) {
-            // Printing a warning message if the input is not a valid octal
-            // number:
-            System.out.println("Invalid Input, Expecting octal number 0-7");
-            return -1;
+        if (inputOctal == null || inputOctal.isEmpty()) {
+            throw new IllegalArgumentException("Input cannot be null or empty");
         }
+
+        int decimalValue = 0;
+
+        for (int i = 0; i < inputOctal.length(); i++) {
+            char currentChar = inputOctal.charAt(i);
+
+            if (currentChar < '0' || currentChar > '7') {
+                throw new IllegalArgumentException("Incorrect input: Expecting an octal number (digits 0-7)");
+            }
+
+            int currentDigit = currentChar - '0';
+            decimalValue = decimalValue * OCTAL_BASE + currentDigit;
+        }
+
+        return decimalValue;
     }
 }

src/main/java/com/thealgorithms/conversions/OctalToHexadecimal.java

@@ -1,63 +1,61 @@
 package com.thealgorithms.conversions;
 
-import java.util.Scanner;
-
 /**
- * Converts any Octal Number to HexaDecimal
+ * Class for converting an Octal number to its Hexadecimal equivalent.
  *
  * @author Tanmay Joshi
  */
-public class OctalToHexadecimal {
+public final class OctalToHexadecimal {
+    private static final int OCTAL_BASE = 8;
+    private static final int HEX_BASE = 16;
+    private static final String HEX_DIGITS = "0123456789ABCDEF";
 
-    /**
-     * This method converts a Octal number to a decimal number
-     *
-     * @param s The Octal Number
-     * @return The Decimal number
-     */
-    public static int octToDec(String s) {
-        int i = 0;
-        for (int j = 0; j < s.length(); j++) {
-            char num = s.charAt(j);
-            num -= '0';
-            i *= 8;
-            i += num;
-        }
-        return i;
+    private OctalToHexadecimal() {
     }
 
     /**
-     * This method converts a Decimal number to a Hexadecimal number
+     * Converts an Octal number (as a string) to its Decimal equivalent.
      *
-     * @param d The Decimal Number
-     * @return The Hexadecimal number
+     * @param octalNumber The Octal number as a string
+     * @return The Decimal equivalent of the Octal number
+     * @throws IllegalArgumentException if the input contains invalid octal digits
      */
-    public static String decimalToHex(int d) {
-        String digits = "0123456789ABCDEF";
-        if (d <= 0) {
+    public static int octalToDecimal(String octalNumber) {
+        if (octalNumber == null || octalNumber.isEmpty()) {
+            throw new IllegalArgumentException("Input cannot be null or empty");
+        }
+
+        int decimalValue = 0;
+        for (int i = 0; i < octalNumber.length(); i++) {
+            char currentChar = octalNumber.charAt(i);
+            if (currentChar < '0' || currentChar > '7') {
+                throw new IllegalArgumentException("Incorrect octal digit: " + currentChar);
+            }
+            int currentDigit = currentChar - '0';
+            decimalValue = decimalValue * OCTAL_BASE + currentDigit;
+        }
+
+        return decimalValue;
+    }
+
+    /**
+     * Converts a Decimal number to its Hexadecimal equivalent.
+     *
+     * @param decimalNumber The Decimal number
+     * @return The Hexadecimal equivalent of the Decimal number
+     */
+    public static String decimalToHexadecimal(int decimalNumber) {
+        if (decimalNumber == 0) {
             return "0";
         }
-        String hex = "";
-        while (d > 0) {
-            int digit = d % 16;
-            hex = digits.charAt(digit) + hex;
-            d = d / 16;
+
+        StringBuilder hexValue = new StringBuilder();
+        while (decimalNumber > 0) {
+            int digit = decimalNumber % HEX_BASE;
+            hexValue.insert(0, HEX_DIGITS.charAt(digit));
+            decimalNumber /= HEX_BASE;
         }
-        return hex;
-    }
 
-    public static void main(String[] args) {
-        Scanner input = new Scanner(System.in);
-        System.out.print("Enter the Octal number: ");
-        // Take octal number as input from user in a string
-        String oct = input.next();
-
-        // Pass the octal number to function and get converted decimal form
-        int decimal = octToDec(oct);
-
-        // Pass the decimal number to function and get converted Hex form of the number
-        String hex = decimalToHex(decimal);
-        System.out.println("The Hexadecimal equivalant is: " + hex);
-        input.close();
+        return hexValue.toString();
     }
 }

src/main/java/com/thealgorithms/conversions/RgbHsvConversion.java

@@ -13,7 +13,9 @@ import java.util.Arrays;
  * (description adapted from <a href="https://en.wikipedia.org/wiki/RGB_color_model">[1]</a> and
  * <a href="https://en.wikipedia.org/wiki/HSL_and_HSV">[2]</a>).
  */
-public class RgbHsvConversion {
+public final class RgbHsvConversion {
+    private RgbHsvConversion() {
+    }
 
     public static void main(String[] args) {
         // Expected RGB-values taken from https://www.rapidtables.com/convert/color/hsv-to-rgb.html

src/main/java/com/thealgorithms/conversions/RomanToInteger.java

@@ -1,12 +1,13 @@
 package com.thealgorithms.conversions;
 
-import java.util.*;
+import java.util.HashMap;
+import java.util.Map;
 
-public class RomanToInteger {
-
-    private static final Map<Character, Integer> map = new HashMap<>() {
-        private static final long serialVersionUID = 87605733047260530L;
+public final class RomanToInteger {
+    private RomanToInteger() {
+    }
 
+    private static final Map<Character, Integer> ROMAN_TO_INT = new HashMap<>() {
         {
             put('I', 1);
             put('V', 5);
@@ -23,31 +24,31 @@ public class RomanToInteger {
     /**
      * This function convert Roman number into Integer
      *
-     * @param A Roman number string
+     * @param a Roman number string
      * @return integer
      */
-    public static int romanToInt(String A) {
-        A = A.toUpperCase();
+    public static int romanToInt(String a) {
+        a = a.toUpperCase();
         char prev = ' ';
 
         int sum = 0;
 
         int newPrev = 0;
-        for (int i = A.length() - 1; i >= 0; i--) {
-            char c = A.charAt(i);
+        for (int i = a.length() - 1; i >= 0; i--) {
+            char c = a.charAt(i);
 
             if (prev != ' ') {
-                // checking current Number greater then previous or not
-                newPrev = map.get(prev) > newPrev ? map.get(prev) : newPrev;
+                // checking current Number greater than previous or not
+                newPrev = ROMAN_TO_INT.get(prev) > newPrev ? ROMAN_TO_INT.get(prev) : newPrev;
             }
 
-            int currentNum = map.get(c);
+            int currentNum = ROMAN_TO_INT.get(c);
 
-            // if current number greater then prev max previous then add
+            // if current number greater than prev max previous then add
             if (currentNum >= newPrev) {
                 sum += currentNum;
             } else {
-                // subtract upcoming number until upcoming number not greater then prev max
+                // subtract upcoming number until upcoming number not greater than prev max
                 sum -= currentNum;
             }
 

src/main/java/com/thealgorithms/conversions/TurkishToLatinConversion.java

@@ -7,7 +7,9 @@ import java.util.Scanner;
  *
  * @author Özgün Gökşenli
  */
-public class TurkishToLatinConversion {
+public final class TurkishToLatinConversion {
+    private TurkishToLatinConversion() {
+    }
 
     /**
      * Main method

src/main/java/com/thealgorithms/conversions/UnitConversions.java

@@ -0,0 +1,14 @@
+package com.thealgorithms.conversions;
+
+import static java.util.Map.entry;
+
+import java.util.Map;
+import org.apache.commons.lang3.tuple.Pair;
+
+public final class UnitConversions {
+    private UnitConversions() {
+    }
+
+    public static final UnitsConverter TEMPERATURE = new UnitsConverter(Map.ofEntries(entry(Pair.of("Kelvin", "Celsius"), new AffineConverter(1.0, -273.15)), entry(Pair.of("Celsius", "Fahrenheit"), new AffineConverter(9.0 / 5.0, 32.0)),
+        entry(Pair.of("Réaumur", "Celsius"), new AffineConverter(5.0 / 4.0, 0.0)), entry(Pair.of("Delisle", "Celsius"), new AffineConverter(-2.0 / 3.0, 100.0)), entry(Pair.of("Rankine", "Kelvin"), new AffineConverter(5.0 / 9.0, 0.0))));
+}

src/main/java/com/thealgorithms/conversions/UnitsConverter.java

@@ -0,0 +1,86 @@
+package com.thealgorithms.conversions;
+
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import org.apache.commons.lang3.tuple.Pair;
+
+public final class UnitsConverter {
+    private final Map<Pair<String, String>, AffineConverter> conversions;
+    private final Set<String> units;
+
+    private static void putIfNeeded(Map<Pair<String, String>, AffineConverter> conversions, final String inputUnit, final String outputUnit, final AffineConverter converter) {
+        if (!inputUnit.equals(outputUnit)) {
+            final var key = Pair.of(inputUnit, outputUnit);
+            conversions.putIfAbsent(key, converter);
+        }
+    }
+
+    private static Map<Pair<String, String>, AffineConverter> addInversions(final Map<Pair<String, String>, AffineConverter> knownConversions) {
+        Map<Pair<String, String>, AffineConverter> res = new HashMap<Pair<String, String>, AffineConverter>();
+        for (final var curConversion : knownConversions.entrySet()) {
+            final var inputUnit = curConversion.getKey().getKey();
+            final var outputUnit = curConversion.getKey().getValue();
+            putIfNeeded(res, inputUnit, outputUnit, curConversion.getValue());
+            putIfNeeded(res, outputUnit, inputUnit, curConversion.getValue().invert());
+        }
+        return res;
+    }
+
+    private static Map<Pair<String, String>, AffineConverter> addCompositions(final Map<Pair<String, String>, AffineConverter> knownConversions) {
+        Map<Pair<String, String>, AffineConverter> res = new HashMap<Pair<String, String>, AffineConverter>();
+        for (final var first : knownConversions.entrySet()) {
+            final var firstKey = first.getKey();
+            putIfNeeded(res, firstKey.getKey(), firstKey.getValue(), first.getValue());
+            for (final var second : knownConversions.entrySet()) {
+                final var secondKey = second.getKey();
+                if (firstKey.getValue().equals(secondKey.getKey())) {
+                    final var newConversion = second.getValue().compose(first.getValue());
+                    putIfNeeded(res, firstKey.getKey(), secondKey.getValue(), newConversion);
+                }
+            }
+        }
+        return res;
+    }
+
+    private static Map<Pair<String, String>, AffineConverter> addAll(final Map<Pair<String, String>, AffineConverter> knownConversions) {
+        final var res = addInversions(knownConversions);
+        return addCompositions(res);
+    }
+
+    private static Map<Pair<String, String>, AffineConverter> computeAllConversions(final Map<Pair<String, String>, AffineConverter> basicConversions) {
+        var tmp = basicConversions;
+        var res = addAll(tmp);
+        while (res.size() != tmp.size()) {
+            tmp = res;
+            res = addAll(tmp);
+        }
+        return res;
+    }
+
+    private static Set<String> extractUnits(final Map<Pair<String, String>, AffineConverter> conversions) {
+        Set<String> res = new HashSet<>();
+        for (final var conversion : conversions.entrySet()) {
+            res.add(conversion.getKey().getKey());
+        }
+        return res;
+    }
+
+    public UnitsConverter(final Map<Pair<String, String>, AffineConverter> basicConversions) {
+        conversions = computeAllConversions(basicConversions);
+        units = extractUnits(conversions);
+    }
+
+    public double convert(final String inputUnit, final String outputUnit, final double value) {
+        if (inputUnit.equals(outputUnit)) {
+            throw new IllegalArgumentException("inputUnit must be different from outputUnit.");
+        }
+        final var conversionKey = Pair.of(inputUnit, outputUnit);
+        return conversions.get(conversionKey).convert(value);
+    }
+
+    public Set<String> availableUnits() {
+        return units;
+    }
+}

src/main/java/com/thealgorithms/datastructures/bags/Bag.java

@@ -4,23 +4,23 @@ import java.util.Iterator;
 import java.util.NoSuchElementException;
 
 /**
- * Collection which does not allow removing elements (only collect and iterate)
+ * A collection that allows adding and iterating over elements but does not support element removal.
  *
- * @param <Element> - the generic type of an element in this bag
+ * @param <E> the type of elements in this bag
  */
-public class Bag<Element> implements Iterable<Element> {
+public class Bag<E> implements Iterable<E> {
 
-    private Node<Element> firstElement; // first element of the bag
-    private int size; // size of bag
+    private Node<E> firstElement; // First element in the bag
+    private int size; // Number of elements in the bag
 
-    private static class Node<Element> {
-
-        private Element content;
-        private Node<Element> nextElement;
+    // Node class representing each element in the bag
+    private static final class Node<E> {
+        private E content;
+        private Node<E> nextElement;
     }
 
     /**
-     * Create an empty bag
+     * Constructs an empty bag.
      */
     public Bag() {
         firstElement = null;
@@ -28,13 +28,17 @@ public class Bag<Element> implements Iterable<Element> {
     }
 
     /**
-     * @return true if this bag is empty, false otherwise
+     * Checks if the bag is empty.
+     *
+     * @return true if the bag is empty, false otherwise
      */
     public boolean isEmpty() {
-        return firstElement == null;
+        return size == 0;
     }
 
     /**
+     * Returns the number of elements in the bag.
+     *
      * @return the number of elements
      */
     public int size() {
@@ -42,24 +46,26 @@ public class Bag<Element> implements Iterable<Element> {
     }
 
     /**
-     * @param element - the element to add
+     * Adds an element to the bag.
+     *
+     * @param element the element to add
      */
-    public void add(Element element) {
-        Node<Element> oldfirst = firstElement;
-        firstElement = new Node<>();
-        firstElement.content = element;
-        firstElement.nextElement = oldfirst;
+    public void add(E element) {
+        Node<E> newNode = new Node<>();
+        newNode.content = element;
+        newNode.nextElement = firstElement;
+        firstElement = newNode;
         size++;
     }
 
     /**
-     * Checks if the bag contains a specific element
+     * Checks if the bag contains a specific element.
      *
-     * @param element which you want to look for
-     * @return true if bag contains element, otherwise false
+     * @param element the element to check for
+     * @return true if the bag contains the element, false otherwise
      */
-    public boolean contains(Element element) {
-        for (Element value : this) {
+    public boolean contains(E element) {
+        for (E value : this) {
             if (value.equals(element)) {
                 return true;
             }
@@ -68,61 +74,37 @@ public class Bag<Element> implements Iterable<Element> {
     }
 
     /**
-     * @return an iterator that iterates over the elements in this bag in
-     * arbitrary order
+     * Returns an iterator over the elements in this bag.
+     *
+     * @return an iterator that iterates over the elements in the bag
      */
-    public Iterator<Element> iterator() {
+    @Override
+    public Iterator<E> iterator() {
         return new ListIterator<>(firstElement);
     }
 
-    @SuppressWarnings("hiding")
-    private class ListIterator<Element> implements Iterator<Element> {
+    // Private class for iterating over elements
+    private static class ListIterator<E> implements Iterator<E> {
 
-        private Node<Element> currentElement;
+        private Node<E> currentElement;
 
-        public ListIterator(Node<Element> firstElement) {
-            currentElement = firstElement;
+        ListIterator(Node<E> firstElement) {
+            this.currentElement = firstElement;
         }
 
+        @Override
         public boolean hasNext() {
             return currentElement != null;
         }
 
-        /**
-         * remove is not allowed in a bag
-         */
         @Override
-        public void remove() {
-            throw new UnsupportedOperationException();
-        }
-
-        public Element next() {
+        public E next() {
             if (!hasNext()) {
                 throw new NoSuchElementException();
             }
-            Element element = currentElement.content;
+            E element = currentElement.content;
             currentElement = currentElement.nextElement;
             return element;
         }
     }
-
-    /**
-     * main-method for testing
-     */
-    public static void main(String[] args) {
-        Bag<String> bag = new Bag<>();
-
-        bag.add("1");
-        bag.add("1");
-        bag.add("2");
-
-        System.out.println("size of bag = " + bag.size());
-        for (String s : bag) {
-            System.out.println(s);
-        }
-
-        System.out.println(bag.contains(null));
-        System.out.println(bag.contains("1"));
-        System.out.println(bag.contains("3"));
-    }
 }

src/main/java/com/thealgorithms/datastructures/bloomfilter/BloomFilter.java

@@ -2,35 +2,61 @@ package com.thealgorithms.datastructures.bloomfilter;
 
 import java.util.BitSet;
 
+/**
+ * A generic BloomFilter implementation for probabilistic membership checking.
+ *
+ * @param <T> The type of elements to be stored in the Bloom filter.
+ */
 public class BloomFilter<T> {
 
-    private int numberOfHashFunctions;
-    private BitSet bitArray;
-    private Hash<T>[] hashFunctions;
+    private final int numberOfHashFunctions;
+    private final BitSet bitArray;
+    private final Hash<T>[] hashFunctions;
 
-    public BloomFilter(int numberOfHashFunctions, int n) {
+    /**
+     * Constructs a BloomFilter with a specified number of hash functions and bit array size.
+     *
+     * @param numberOfHashFunctions the number of hash functions to use
+     * @param bitArraySize          the size of the bit array
+     */
+    @SuppressWarnings("unchecked")
+    public BloomFilter(int numberOfHashFunctions, int bitArraySize) {
         this.numberOfHashFunctions = numberOfHashFunctions;
-        hashFunctions = new Hash[numberOfHashFunctions];
-        bitArray = new BitSet(n);
-        insertHash();
+        this.bitArray = new BitSet(bitArraySize);
+        this.hashFunctions = new Hash[numberOfHashFunctions];
+        initializeHashFunctions();
     }
 
-    private void insertHash() {
+    /**
+     * Initializes the hash functions with unique indices.
+     */
+    private void initializeHashFunctions() {
         for (int i = 0; i < numberOfHashFunctions; i++) {
-            hashFunctions[i] = new Hash(i);
+            hashFunctions[i] = new Hash<>(i);
         }
     }
 
+    /**
+     * Inserts an element into the Bloom filter.
+     *
+     * @param key the element to insert
+     */
     public void insert(T key) {
         for (Hash<T> hash : hashFunctions) {
-            int position = hash.compute(key) % bitArray.size();
+            int position = Math.abs(hash.compute(key) % bitArray.size());
             bitArray.set(position);
         }
     }
 
+    /**
+     * Checks if an element might be in the Bloom filter.
+     *
+     * @param key the element to check
+     * @return {@code true} if the element might be in the Bloom filter, {@code false} if it is definitely not
+     */
     public boolean contains(T key) {
         for (Hash<T> hash : hashFunctions) {
-            int position = hash.compute(key) % bitArray.size();
+            int position = Math.abs(hash.compute(key) % bitArray.size());
             if (!bitArray.get(position)) {
                 return false;
             }
@@ -38,24 +64,46 @@ public class BloomFilter<T> {
         return true;
     }
 
-    private class Hash<T> {
+    /**
+     * Inner class representing a hash function used by the Bloom filter.
+     *
+     * @param <T> The type of elements to be hashed.
+     */
+    private static class Hash<T> {
 
-        int index;
+        private final int index;
 
-        public Hash(int index) {
+        /**
+         * Constructs a Hash function with a specified index.
+         *
+         * @param index the index of this hash function
+         */
+        Hash(int index) {
             this.index = index;
         }
 
+        /**
+         * Computes the hash of the given key.
+         *
+         * @param key the element to hash
+         * @return the hash value
+         */
         public int compute(T key) {
             return index * asciiString(String.valueOf(key));
         }
 
+        /**
+         * Computes the ASCII value sum of the characters in a string.
+         *
+         * @param word the string to compute
+         * @return the sum of ASCII values of the characters
+         */
         private int asciiString(String word) {
-            int number = 0;
-            for (int i = 0; i < word.length(); i++) {
-                number += word.charAt(i);
+            int sum = 0;
+            for (char c : word.toCharArray()) {
+                sum += c;
             }
-            return number;
+            return sum;
         }
     }
 }

src/main/java/com/thealgorithms/datastructures/buffers/CircularBuffer.java

@@ -24,7 +24,9 @@ public class CircularBuffer<Item> {
     }
 
     public Item get() {
-        if (isEmpty()) return null;
+        if (isEmpty()) {
+            return null;
+        }
 
         Item item = buffer[getPointer.getAndIncrement()];
         size.decrementAndGet();
@@ -32,7 +34,9 @@ public class CircularBuffer<Item> {
     }
 
     public boolean put(Item item) {
-        if (isFull()) return false;
+        if (isFull()) {
+            return false;
+        }
 
         buffer[putPointer.getAndIncrement()] = item;
         size.incrementAndGet();
@@ -43,13 +47,15 @@ public class CircularBuffer<Item> {
         private int pointer;
         private final int max;
 
-        public CircularPointer(int pointer, int max) {
+        CircularPointer(int pointer, int max) {
             this.pointer = pointer;
             this.max = max;
         }
 
         public int getAndIncrement() {
-            if (pointer == max) pointer = 0;
+            if (pointer == max) {
+                pointer = 0;
+            }
             int tmp = pointer;
             pointer++;
             return tmp;

src/main/java/com/thealgorithms/datastructures/caches/LFUCache.java

@@ -10,14 +10,13 @@ import java.util.Map;
 public class LFUCache<K, V> {
 
     private class Node {
-
-        private K key;
+        private final K key;
         private V value;
         private int frequency;
         private Node previous;
         private Node next;
 
-        public Node(K key, V value, int frequency) {
+        Node(K key, V value, int frequency) {
             this.key = key;
             this.value = value;
             this.frequency = frequency;
@@ -26,67 +25,67 @@ public class LFUCache<K, V> {
 
     private Node head;
     private Node tail;
-    private Map<K, Node> map = null;
-    private Integer capacity;
+    private final Map<K, Node> cache;
+    private final int capacity;
     private static final int DEFAULT_CAPACITY = 100;
 
     public LFUCache() {
-        this.capacity = DEFAULT_CAPACITY;
+        this(DEFAULT_CAPACITY);
     }
 
-    public LFUCache(Integer capacity) {
+    public LFUCache(int capacity) {
+        if (capacity <= 0) {
+            throw new IllegalArgumentException("Capacity must be greater than zero.");
+        }
         this.capacity = capacity;
-        this.map = new HashMap<>();
+        this.cache = new HashMap<>();
     }
 
     /**
-     * This method returns value present in the cache corresponding to the key passed as parameter
+     * Retrieves the value for the given key from the cache. Increases the frequency of the node.
      *
-     * @param <K> key for which value is to be retrieved
-     * @returns <V> object corresponding to the key passed as parameter, returns null if <K> key is
-     *     not present in the cache
+     * @param key The key to look up.
+     * @return The value associated with the key, or null if the key is not present.
      */
     public V get(K key) {
-        if (this.map.get(key) == null) {
+        Node node = cache.get(key);
+        if (node == null) {
             return null;
         }
-
-        Node node = map.get(key);
         removeNode(node);
         node.frequency += 1;
         addNodeWithUpdatedFrequency(node);
-
         return node.value;
     }
 
     /**
-     * This method stores <K> key and <V> value in the cache
+     * Adds or updates a key-value pair in the cache. If the cache is full, the least frequently used item is evicted.
      *
-     * @param <K> key which is to be stored in the cache
-     * @param <V> value which is to be stored in the cache
+     * @param key   The key to insert or update.
+     * @param value The value to insert or update.
      */
     public void put(K key, V value) {
-        if (map.containsKey(key)) {
-            Node node = map.get(key);
+        if (cache.containsKey(key)) {
+            Node node = cache.get(key);
             node.value = value;
             node.frequency += 1;
             removeNode(node);
             addNodeWithUpdatedFrequency(node);
         } else {
-            if (map.size() >= capacity) {
-                map.remove(this.head.key);
+            if (cache.size() >= capacity) {
+                cache.remove(this.head.key);
                 removeNode(head);
             }
             Node node = new Node(key, value, 1);
             addNodeWithUpdatedFrequency(node);
-            map.put(key, node);
+            cache.put(key, node);
         }
     }
 
     /**
-     * This method stores the node in the cache with updated frequency
+     * Adds a node to the linked list in the correct position based on its frequency.
      *
-     * @param Node node which is to be updated in the cache
+     * @param node The node to add.
      */
     private void addNodeWithUpdatedFrequency(Node node) {
         if (tail != null && head != null) {
@@ -123,9 +122,9 @@ public class LFUCache<K, V> {
     }
 
     /**
-     * This method removes node from the cache
+     * Removes a node from the linked list.
      *
-     * @param Node node which is to be removed in the cache
+     * @param node The node to remove.
      */
     private void removeNode(Node node) {
         if (node.previous != null) {

src/main/java/com/thealgorithms/datastructures/caches/LRUCache.java

@@ -126,10 +126,10 @@ public class LRUCache<K, V> {
         private I key;
         private J value;
 
-        public Entry() {
+        Entry() {
         }
 
-        public Entry(Entry<I, J> preEntry, Entry<I, J> nextEntry, I key, J value) {
+        Entry(Entry<I, J> preEntry, Entry<I, J> nextEntry, I key, J value) {
             this.preEntry = preEntry;
             this.nextEntry = nextEntry;
             this.key = key;

src/main/java/com/thealgorithms/datastructures/caches/MRUCache.java

@@ -124,10 +124,10 @@ public class MRUCache<K, V> {
         private I key;
         private J value;
 
-        public Entry() {
+        Entry() {
         }
 
-        public Entry(Entry<I, J> preEntry, Entry<I, J> nextEntry, I key, J value) {
+        Entry(Entry<I, J> preEntry, Entry<I, J> nextEntry, I key, J value) {
             this.preEntry = preEntry;
             this.nextEntry = nextEntry;
             this.key = key;

src/main/java/com/thealgorithms/datastructures/crdt/GCounter.java

@@ -17,7 +17,7 @@ import java.util.Map;
  */
 
 class GCounter {
-    private final Map<Integer, Integer> P;
+    private final Map<Integer, Integer> counterMap;
     private final int myId;
     private final int n;
 
@@ -26,13 +26,13 @@ class GCounter {
      *
      * @param n The number of nodes in the cluster.
      */
-    public GCounter(int myId, int n) {
+    GCounter(int myId, int n) {
         this.myId = myId;
         this.n = n;
-        this.P = new HashMap<>();
+        this.counterMap = new HashMap<>();
 
         for (int i = 0; i < n; i++) {
-            P.put(i, 0);
+            counterMap.put(i, 0);
         }
     }
 
@@ -40,7 +40,7 @@ class GCounter {
      * Increments the counter for the current node.
      */
     public void increment() {
-        P.put(myId, P.get(myId) + 1);
+        counterMap.put(myId, counterMap.get(myId) + 1);
     }
 
     /**
@@ -50,7 +50,7 @@ class GCounter {
      */
     public int value() {
         int sum = 0;
-        for (int v : P.values()) {
+        for (int v : counterMap.values()) {
             sum += v;
         }
         return sum;
@@ -64,7 +64,7 @@ class GCounter {
      */
     public boolean compare(GCounter other) {
         for (int i = 0; i < n; i++) {
-            if (this.P.get(i) > other.P.get(i)) {
+            if (this.counterMap.get(i) > other.counterMap.get(i)) {
                 return false;
             }
         }
@@ -78,7 +78,7 @@ class GCounter {
      */
     public void merge(GCounter other) {
         for (int i = 0; i < n; i++) {
-            this.P.put(i, Math.max(this.P.get(i), other.P.get(i)));
+            this.counterMap.put(i, Math.max(this.counterMap.get(i), other.counterMap.get(i)));
         }
     }
 }

src/main/java/com/thealgorithms/datastructures/crdt/LWWElementSet.java

@@ -26,7 +26,7 @@ class Element {
      * @param timestamp The timestamp associated with the element.
      * @param bias      The bias of the element (ADDS or REMOVALS).
      */
-    public Element(String key, int timestamp, Bias bias) {
+    Element(String key, int timestamp, Bias bias) {
         this.key = key;
         this.timestamp = timestamp;
         this.bias = bias;
@@ -49,7 +49,7 @@ class LWWElementSet {
     /**
      * Constructs an empty LWWElementSet.
      */
-    public LWWElementSet() {
+    LWWElementSet() {
         this.addSet = new HashMap<>();
         this.removeSet = new HashMap<>();
     }
@@ -124,14 +124,14 @@ class LWWElementSet {
      * @return True if the first element's timestamp is greater or the bias is ADDS and timestamps are equal.
      */
     public boolean compareTimestamps(Element e, Element other) {
-        if (!e.bias.equals(other.bias)) {
+        if (e.bias != other.bias) {
             throw new IllegalArgumentException("Invalid bias value");
         }
         Bias bias = e.bias;
         int timestampComparison = Integer.compare(e.timestamp, other.timestamp);
 
         if (timestampComparison == 0) {
-            return !bias.equals(Bias.ADDS);
+            return bias != Bias.ADDS;
         }
         return timestampComparison < 0;
     }

src/main/java/com/thealgorithms/datastructures/crdt/PNCounter.java

@@ -17,8 +17,8 @@ import java.util.Map;
  */
 
 class PNCounter {
-    private final Map<Integer, Integer> P;
-    private final Map<Integer, Integer> N;
+    private final Map<Integer, Integer> pCounter;
+    private final Map<Integer, Integer> nCounter;
     private final int myId;
     private final int n;
 
@@ -28,15 +28,15 @@ class PNCounter {
      * @param myId The identifier of the current node.
      * @param n    The number of nodes in the cluster.
      */
-    public PNCounter(int myId, int n) {
+    PNCounter(int myId, int n) {
         this.myId = myId;
         this.n = n;
-        this.P = new HashMap<>();
-        this.N = new HashMap<>();
+        this.pCounter = new HashMap<>();
+        this.nCounter = new HashMap<>();
 
         for (int i = 0; i < n; i++) {
-            P.put(i, 0);
-            N.put(i, 0);
+            pCounter.put(i, 0);
+            nCounter.put(i, 0);
         }
     }
 
@@ -44,14 +44,14 @@ class PNCounter {
      * Increments the increment counter for the current node.
      */
     public void increment() {
-        P.put(myId, P.get(myId) + 1);
+        pCounter.put(myId, pCounter.get(myId) + 1);
     }
 
     /**
      * Increments the decrement counter for the current node.
      */
     public void decrement() {
-        N.put(myId, N.get(myId) + 1);
+        nCounter.put(myId, nCounter.get(myId) + 1);
     }
 
     /**
@@ -60,8 +60,8 @@ class PNCounter {
      * @return The total value of the counter.
      */
     public int value() {
-        int sumP = P.values().stream().mapToInt(Integer::intValue).sum();
-        int sumN = N.values().stream().mapToInt(Integer::intValue).sum();
+        int sumP = pCounter.values().stream().mapToInt(Integer::intValue).sum();
+        int sumN = nCounter.values().stream().mapToInt(Integer::intValue).sum();
         return sumP - sumN;
     }
 
@@ -76,7 +76,7 @@ class PNCounter {
             throw new IllegalArgumentException("Cannot compare PN-Counters with different number of nodes");
         }
         for (int i = 0; i < n; i++) {
-            if (this.P.get(i) > other.P.get(i) && this.N.get(i) > other.N.get(i)) {
+            if (this.pCounter.get(i) > other.pCounter.get(i) && this.nCounter.get(i) > other.nCounter.get(i)) {
                 return false;
             }
         }
@@ -93,8 +93,8 @@ class PNCounter {
             throw new IllegalArgumentException("Cannot merge PN-Counters with different number of nodes");
         }
         for (int i = 0; i < n; i++) {
-            this.P.put(i, Math.max(this.P.get(i), other.P.get(i)));
-            this.N.put(i, Math.max(this.N.get(i), other.N.get(i)));
+            this.pCounter.put(i, Math.max(this.pCounter.get(i), other.pCounter.get(i)));
+            this.nCounter.put(i, Math.max(this.nCounter.get(i), other.nCounter.get(i)));
         }
     }
 }

src/main/java/com/thealgorithms/datastructures/dynamicarray/DynamicArray.java

@@ -1,222 +1,204 @@
 package com.thealgorithms.datastructures.dynamicarray;
 
-import java.util.*;
+import java.util.Arrays;
+import java.util.ConcurrentModificationException;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import java.util.Objects;
 import java.util.function.Consumer;
 import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
 
 /**
- * This class implements a dynamic array
+ * This class implements a dynamic array.
  *
  * @param <E> the type that each index of the array will hold
  */
 public class DynamicArray<E> implements Iterable<E> {
 
     private static final int DEFAULT_CAPACITY = 16;
-
-    private int capacity;
     private int size;
+    private int modCount; // Tracks structural modifications for the iterator
     private Object[] elements;
 
     /**
-     * constructor
+     * Constructor with initial capacity.
      *
      * @param capacity the starting length of the desired array
+     * @throws IllegalArgumentException if the specified capacity is negative
      */
     public DynamicArray(final int capacity) {
+        if (capacity < 0) {
+            throw new IllegalArgumentException("Capacity cannot be negative.");
+        }
         this.size = 0;
-        this.capacity = capacity;
-        this.elements = new Object[this.capacity];
+        this.modCount = 0;
+        this.elements = new Object[capacity];
     }
 
     /**
-     * No-args constructor
+     * No-args constructor with default capacity.
      */
     public DynamicArray() {
         this(DEFAULT_CAPACITY);
     }
 
     /**
-     * Adds an element to the array If full, creates a copy array twice the size
-     * of the current one
+     * Adds an element to the array. If full, creates a new array with double the size.
      *
-     * @param element the element of type <E> to be added to the array
+     * @param element the element to be added to the array
      */
     public void add(final E element) {
-        if (this.size == this.elements.length) {
-            this.elements = Arrays.copyOf(this.elements, newCapacity(2 * this.capacity));
-        }
-
-        this.elements[this.size] = element;
-        size++;
+        ensureCapacity(size + 1);
+        elements[size++] = element;
+        modCount++; // Increment modification count
     }
 
     /**
-     * Places element of type <E> at the desired index
+     * Places an element at the desired index, expanding capacity if necessary.
      *
-     * @param index the index for the element to be placed
+     * @param index   the index for the element to be placed
      * @param element the element to be inserted
+     * @throws IndexOutOfBoundsException if n is less than 0 or greater or equal to the number of elements in the array
      */
     public void put(final int index, E element) {
-        this.elements[index] = element;
+        if (index < 0) {
+            throw new IndexOutOfBoundsException("Index cannot be negative.");
+        }
+        ensureCapacity(index + 1);
+        elements[index] = element;
+        if (index >= size) {
+            size = index + 1;
+        }
+        modCount++; // Increment modification count
     }
 
     /**
-     * get method for element at a given index returns null if the index is
-     * empty
+     * Gets the element at a given index.
      *
      * @param index the desired index of the element
-     * @return <E> the element at the specified index
+     * @return the element at the specified index
+     * @throws IndexOutOfBoundsException if n is less than 0 or greater or equal to the number of elements in the array
      */
+    @SuppressWarnings("unchecked")
     public E get(final int index) {
-        return getElement(index);
+        if (index < 0 || index >= size) {
+            throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);
+        }
+        return (E) elements[index];
     }
 
     /**
-     * Removes an element from the array
+     * Removes an element from the array.
      *
      * @param index the index of the element to be removed
-     * @return <E> the element removed
+     * @return the element removed
+     * @throws IndexOutOfBoundsException if n is less than 0 or greater or equal to the number of elements in the array
      */
     public E remove(final int index) {
-        final E oldElement = getElement(index);
-        fastRemove(this.elements, index);
-
-        if (this.capacity > DEFAULT_CAPACITY && size * 4 <= this.capacity) {
-            this.elements = Arrays.copyOf(this.elements, newCapacity(this.capacity / 2));
+        if (index < 0 || index >= size) {
+            throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);
         }
+        @SuppressWarnings("unchecked") E oldElement = (E) elements[index];
+        fastRemove(index);
+        modCount++; // Increment modification count
         return oldElement;
     }
 
     /**
-     * get method for size field
+     * Gets the size of the array.
      *
-     * @return int size
+     * @return the size
      */
     public int getSize() {
-        return this.size;
+        return size;
     }
 
     /**
-     * isEmpty helper method
+     * Checks if the array is empty.
      *
-     * @return boolean true if the array contains no elements, false otherwise
+     * @return true if the array contains no elements, false otherwise
      */
     public boolean isEmpty() {
-        return this.size == 0;
+        return size == 0;
     }
 
     public Stream<E> stream() {
         return StreamSupport.stream(spliterator(), false);
     }
 
-    private void fastRemove(final Object[] elements, final int index) {
-        final int newSize = this.size - 1;
-
-        if (newSize > index) {
-            System.arraycopy(elements, index + 1, elements, index, newSize - index);
+    private void ensureCapacity(int minCapacity) {
+        if (minCapacity > elements.length) {
+            int newCapacity = Math.max(elements.length * 2, minCapacity);
+            elements = Arrays.copyOf(elements, newCapacity);
         }
-
-        elements[this.size = newSize] = null;
     }
 
-    private E getElement(final int index) {
-        return (E) this.elements[index];
+    private void fastRemove(int index) {
+        int numMoved = size - index - 1;
+        if (numMoved > 0) {
+            System.arraycopy(elements, index + 1, elements, index, numMoved);
+        }
+        elements[--size] = null; // Clear to let GC do its work
     }
 
-    private int newCapacity(int capacity) {
-        this.capacity = capacity;
-        return this.capacity;
-    }
-
-    /**
-     * returns a String representation of this object
-     *
-     * @return String a String representing the array
-     */
     @Override
     public String toString() {
-        return Arrays.toString(Arrays.stream(this.elements).filter(Objects::nonNull).toArray());
+        return Arrays.toString(Arrays.copyOf(elements, size));
     }
 
-    /**
-     * Creates and returns a new Dynamic Array Iterator
-     *
-     * @return Iterator a Dynamic Array Iterator
-     */
     @Override
     public Iterator<E> iterator() {
         return new DynamicArrayIterator();
     }
 
-    private class DynamicArrayIterator implements Iterator<E> {
+    private final class DynamicArrayIterator implements Iterator<E> {
 
         private int cursor;
+        private int expectedModCount;
 
-        @Override
-        public boolean hasNext() {
-            return this.cursor != size;
+        DynamicArrayIterator() {
+            this.expectedModCount = modCount;
         }
 
         @Override
+        public boolean hasNext() {
+            checkForComodification();
+            return cursor < size;
+        }
+
+        @Override
+        @SuppressWarnings("unchecked")
         public E next() {
-            if (this.cursor > DynamicArray.this.size) {
+            checkForComodification();
+            if (cursor >= size) {
                 throw new NoSuchElementException();
             }
-
-            if (this.cursor > DynamicArray.this.elements.length) {
-                throw new ConcurrentModificationException();
-            }
-
-            final E element = DynamicArray.this.getElement(this.cursor);
-            this.cursor++;
-
-            return element;
+            return (E) elements[cursor++];
         }
 
         @Override
         public void remove() {
-            if (this.cursor < 0) {
+            if (cursor <= 0) {
                 throw new IllegalStateException();
             }
+            checkForComodification();
+            DynamicArray.this.remove(--cursor);
+            expectedModCount = ++modCount;
+        }
 
-            DynamicArray.this.remove(this.cursor);
-            this.cursor--;
+        private void checkForComodification() {
+            if (modCount != expectedModCount) {
+                throw new ConcurrentModificationException();
+            }
         }
 
         @Override
         public void forEachRemaining(Consumer<? super E> action) {
             Objects.requireNonNull(action);
-
-            for (int i = 0; i < DynamicArray.this.size; i++) {
-                action.accept(DynamicArray.this.getElement(i));
+            while (hasNext()) {
+                action.accept(next());
             }
         }
     }
-
-    /**
-     * This class is the driver for the DynamicArray<E> class it tests a variety
-     * of methods and prints the output
-     */
-    public static void main(String[] args) {
-        DynamicArray<String> names = new DynamicArray<>();
-        names.add("Peubes");
-        names.add("Marley");
-
-        for (String name : names) {
-            System.out.println(name);
-        }
-
-        names.stream().forEach(System.out::println);
-
-        System.out.println(names);
-
-        System.out.println(names.getSize());
-
-        names.remove(0);
-
-        for (String name : names) {
-            System.out.println(name);
-        }
-    }
 }

src/main/java/com/thealgorithms/datastructures/graphs/AStar.java

@@ -3,9 +3,15 @@
  */
 package com.thealgorithms.datastructures.graphs;
 
-import java.util.*;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.List;
+import java.util.PriorityQueue;
 
-public class A_Star {
+public final class AStar {
+    private AStar() {
+    }
 
     private static class Graph {
 
@@ -14,7 +20,7 @@ public class A_Star {
         private ArrayList<ArrayList<Edge>> graph;
 
         // Initialise ArrayLists in Constructor
-        public Graph(int size) {
+        Graph(int size) {
             this.graph = new ArrayList<>();
             for (int i = 0; i < size; i++) {
                 this.graph.add(new ArrayList<>());
@@ -38,7 +44,7 @@ public class A_Star {
         private int to;
         private int weight;
 
-        public Edge(int from, int to, int weight) {
+        Edge(int from, int to, int weight) {
             this.from = from;
             this.to = to;
             this.weight = weight;
@@ -64,7 +70,7 @@ public class A_Star {
         private ArrayList<Integer> path; // list of visited nodes in this path.
         private int estimated; // heuristic value associated to the last node od the path (current node).
 
-        public PathAndDistance(int distance, ArrayList<Integer> path, int estimated) {
+        PathAndDistance(int distance, ArrayList<Integer> path, int estimated) {
             this.distance = distance;
             this.path = path;
             this.estimated = estimated;

src/main/java/com/thealgorithms/datastructures/graphs/BellmanFord.java

@@ -1,6 +1,6 @@
 package com.thealgorithms.datastructures.graphs;
 
-import java.util.*;
+import java.util.Scanner;
 
 class BellmanFord /*
                    * Implementation of Bellman ford to detect negative cycles. Graph accepts
@@ -11,7 +11,8 @@ class BellmanFord /*
                    */
 {
 
-    int vertex, edge;
+    int vertex;
+    int edge;
     private Edge[] edges;
     private int index = 0;
 
@@ -23,7 +24,8 @@ class BellmanFord /*
 
     class Edge {
 
-        int u, v;
+        int u;
+        int v;
         int w;
 
         /**
@@ -31,7 +33,7 @@ class BellmanFord /*
          * @param v End vertex
          * @param c Weight
          */
-        public Edge(int a, int b, int c) {
+        Edge(int a, int b, int c) {
             u = a;
             v = b;
             w = c;
@@ -55,10 +57,19 @@ class BellmanFord /*
         obj.go();
     }
 
-    public void go() { // shows distance to all vertices // Interactive run for understanding the
-        try ( // class first time. Assumes source vertex is 0 and
-            Scanner sc = new Scanner(System.in)) {
-            int i, v, e, u, ve, w, j, neg = 0;
+    public void go() {
+        // shows distance to all vertices
+        // Interactive run for understanding the
+        // class first time. Assumes source vertex is 0 and
+        try (Scanner sc = new Scanner(System.in)) {
+            int i;
+            int v;
+            int e;
+            int u;
+            int ve;
+            int w;
+            int j;
+            int neg = 0;
             System.out.println("Enter no. of vertices and edges please");
             v = sc.nextInt();
             e = sc.nextInt();
@@ -107,7 +118,6 @@ class BellmanFord /*
                     System.out.println();
                 }
             }
-            sc.close();
         }
     }
 
@@ -120,7 +130,11 @@ class BellmanFord /*
         Edge[] arr) { // be created by using addEdge() method and passed by calling getEdgeArray()
                       // method // Just shows results of computation, if graph is passed to it. The
                       // graph should
-        int i, j, v = vertex, e = edge, neg = 0;
+        int i;
+        int j;
+        int v = vertex;
+        int e = edge;
+        int neg = 0;
         double[] dist = new double[v]; // Distance array for holding the finalized shortest path
                                        // distance between source
         // and all vertices

src/main/java/com/thealgorithms/datastructures/graphs/BipartiteGraphDFS.java

@@ -14,16 +14,18 @@ import java.util.Arrays;
  *
  * Output : YES
  */
-public class BipartiteGrapfDFS {
+public final class BipartiteGraphDFS {
+    private BipartiteGraphDFS() {
+    }
 
-    private static boolean bipartite(int V, ArrayList<ArrayList<Integer>> adj, int[] color, int node) {
+    private static boolean bipartite(int v, ArrayList<ArrayList<Integer>> adj, int[] color, int node) {
         if (color[node] == -1) {
             color[node] = 1;
         }
         for (Integer it : adj.get(node)) {
             if (color[it] == -1) {
                 color[it] = 1 - color[node];
-                if (!bipartite(V, adj, color, it)) {
+                if (!bipartite(v, adj, color, it)) {
                     return false;
                 }
             } else if (color[it] == color[node]) {
@@ -33,14 +35,14 @@ public class BipartiteGrapfDFS {
         return true;
     }
 
-    public static boolean isBipartite(int V, ArrayList<ArrayList<Integer>> adj) {
+    public static boolean isBipartite(int v, ArrayList<ArrayList<Integer>> adj) {
         // Code here
-        int[] color = new int[V + 1];
+        int[] color = new int[v + 1];
         Arrays.fill(color, -1);
 
-        for (int i = 0; i < V; i++) {
+        for (int i = 0; i < v; i++) {
             if (color[i] == -1) {
-                if (!bipartite(V, adj, color, i)) {
+                if (!bipartite(v, adj, color, i)) {
                     return false;
                 }
             }
@@ -52,23 +54,23 @@ public class BipartiteGrapfDFS {
         BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
         int t = Integer.parseInt(read.readLine().trim());
         while (t-- > 0) {
-            String[] S = read.readLine().trim().split(" ");
-            int V = Integer.parseInt(S[0]);
-            int E = Integer.parseInt(S[1]);
+            String[] str1 = read.readLine().trim().split(" ");
+            int numVertices = Integer.parseInt(str1[0]);
+            int numEdges = Integer.parseInt(str1[1]);
 
             ArrayList<ArrayList<Integer>> adj = new ArrayList<>();
-            for (int i = 0; i < V; i++) {
+            for (int i = 0; i < numVertices; i++) {
                 adj.add(new ArrayList<>());
             }
-            for (int i = 0; i < E; i++) {
-                String[] s = read.readLine().trim().split(" ");
-                int u = Integer.parseInt(s[0]);
-                int v = Integer.parseInt(s[1]);
-                adj.get(u).add(v);
-                adj.get(v).add(u);
+            for (int i = 0; i < numEdges; i++) {
+                String[] str2 = read.readLine().trim().split(" ");
+                int vertexU = Integer.parseInt(str2[0]);
+                int vertexV = Integer.parseInt(str2[1]);
+                adj.get(vertexU).add(vertexV);
+                adj.get(vertexV).add(vertexU);
             }
 
-            boolean ans = isBipartite(V, adj);
+            boolean ans = isBipartite(numVertices, adj);
             if (ans) {
                 System.out.println("YES");
             } else {

src/main/java/com/thealgorithms/datastructures/graphs/ConnectedComponent.java

@@ -15,16 +15,17 @@ class Graph<E extends Comparable<E>> {
 
         E name;
 
-        public Node(E name) {
+        Node(E name) {
             this.name = name;
         }
     }
 
     class Edge {
 
-        Node startNode, endNode;
+        Node startNode;
+        Node endNode;
 
-        public Edge(Node startNode, Node endNode) {
+        Edge(Node startNode, Node endNode) {
             this.startNode = startNode;
             this.endNode = endNode;
         }
@@ -33,7 +34,7 @@ class Graph<E extends Comparable<E>> {
     ArrayList<Edge> edgeList;
     ArrayList<Node> nodeList;
 
-    public Graph() {
+    Graph() {
         edgeList = new ArrayList<Edge>();
         nodeList = new ArrayList<Node>();
     }
@@ -46,7 +47,8 @@ class Graph<E extends Comparable<E>> {
      * @param endNode the ending Node from the edge
      */
     public void addEdge(E startNode, E endNode) {
-        Node start = null, end = null;
+        Node start = null;
+        Node end = null;
         for (Node node : nodeList) {
             if (startNode.compareTo(node.name) == 0) {
                 start = node;
@@ -79,8 +81,7 @@ class Graph<E extends Comparable<E>> {
         Set<Node> markedNodes = new HashSet<Node>();
 
         for (Node n : nodeList) {
-            if (!markedNodes.contains(n)) {
-                markedNodes.add(n);
+            if (markedNodes.add(n)) {
                 markedNodes.addAll(depthFirstSearch(n, new ArrayList<Node>()));
                 count++;
             }
@@ -107,7 +108,9 @@ class Graph<E extends Comparable<E>> {
     }
 }
 
-public class ConnectedComponent {
+public final class ConnectedComponent {
+    private ConnectedComponent() {
+    }
 
     public static void main(String[] args) {
         Graph<Character> graphChars = new Graph<>();

src/main/java/com/thealgorithms/datastructures/graphs/Cycles.java

@@ -5,12 +5,13 @@ import java.util.Scanner;
 
 class Cycle {
 
-    private int nodes, edges;
+    private final int nodes;
+    private final int edges;
     private int[][] adjacencyMatrix;
     private boolean[] visited;
     ArrayList<ArrayList<Integer>> cycles = new ArrayList<ArrayList<Integer>>();
 
-    public Cycle() {
+    Cycle() {
         Scanner in = new Scanner(System.in);
         System.out.print("Enter the no. of nodes: ");
         nodes = in.nextInt();
@@ -27,7 +28,8 @@ class Cycle {
         System.out.println("Enter the details of each edges <Start Node> <End Node>");
 
         for (int i = 0; i < edges; i++) {
-            int start, end;
+            int start;
+            int end;
             start = in.nextInt();
             end = in.nextInt();
             adjacencyMatrix[start][end] = 1;
@@ -78,7 +80,9 @@ class Cycle {
     }
 }
 
-public class Cycles {
+public final class Cycles {
+    private Cycles() {
+    }
 
     public static void main(String[] args) {
         Cycle c = new Cycle();

src/main/java/com/thealgorithms/datastructures/graphs/DIJSKSTRAS_ALGORITHM.java

@@ -1,85 +0,0 @@
-/*
-Refer https://www.geeksforgeeks.org/dijkstras-shortest-path-algorithm-greedy-algo-7/
-for better understanding
- */
-package com.thealgorithms.datastructures.graphs;
-
-class dijkstras {
-
-    int k = 9;
-
-    int minDist(int[] dist, Boolean[] Set) {
-        int min = Integer.MAX_VALUE, min_index = -1;
-
-        for (int r = 0; r < k; r++) {
-            if (!Set[r] && dist[r] <= min) {
-                min = dist[r];
-                min_index = r;
-            }
-        }
-
-        return min_index;
-    }
-
-    void print(int[] dist) {
-        System.out.println("Vertex \t\t Distance");
-        for (int i = 0; i < k; i++) {
-            System.out.println(i + " \t " + dist[i]);
-        }
-    }
-
-    void dijkstra(int[][] graph, int src) {
-        int[] dist = new int[k];
-        Boolean[] Set = new Boolean[k];
-
-        for (int i = 0; i < k; i++) {
-            dist[i] = Integer.MAX_VALUE;
-            Set[i] = false;
-        }
-
-        dist[src] = 0;
-
-        for (int c = 0; c < k - 1; c++) {
-            int u = minDist(dist, Set);
-
-            Set[u] = true;
-
-            for (int v = 0; v < k; v++) {
-                if (!Set[v] && graph[u][v] != 0 && dist[u] != Integer.MAX_VALUE && dist[u] + graph[u][v] < dist[v]) {
-                    dist[v] = dist[u] + graph[u][v];
-                }
-            }
-        }
-
-        print(dist);
-    }
-
-    public static void main(String[] args) {
-        int[][] graph = new int[][] {
-            {0, 4, 0, 0, 0, 0, 0, 8, 0},
-            {4, 0, 8, 0, 0, 0, 0, 11, 0},
-            {0, 8, 0, 7, 0, 4, 0, 0, 2},
-            {0, 0, 7, 0, 9, 14, 0, 0, 0},
-            {0, 0, 0, 9, 0, 10, 0, 0, 0},
-            {0, 0, 4, 14, 10, 0, 2, 0, 0},
-            {0, 0, 0, 0, 0, 2, 0, 1, 6},
-            {8, 11, 0, 0, 0, 0, 1, 0, 7},
-            {0, 0, 2, 0, 0, 0, 6, 7, 0},
-        };
-        dijkstras t = new dijkstras();
-        t.dijkstra(graph, 0);
-    } // main
-} // djikstras
-/*
-OUTPUT :
-Vertex   Distance
-0            0
-1            4
-2            12
-3            19
-4            21
-5            11
-6            9
-7            8
-8            14
- */

src/main/java/com/thealgorithms/datastructures/graphs/DijkstraAlgorithm.java

@@ -0,0 +1,91 @@
+package com.thealgorithms.datastructures.graphs;
+
+import java.util.Arrays;
+
+/**
+ * Dijkstra's algorithm for finding the shortest path from a single source vertex to all other vertices in a graph.
+ */
+public class DijkstraAlgorithm {
+
+    private final int vertexCount;
+
+    /**
+     * Constructs a Dijkstra object with the given number of vertices.
+     *
+     * @param vertexCount The number of vertices in the graph.
+     */
+    public DijkstraAlgorithm(int vertexCount) {
+        this.vertexCount = vertexCount;
+    }
+
+    /**
+     * Executes Dijkstra's algorithm on the provided graph to find the shortest paths from the source vertex to all other vertices.
+     *
+     * The graph is represented as an adjacency matrix where {@code graph[i][j]} represents the weight of the edge from vertex {@code i}
+     * to vertex {@code j}. A value of 0 indicates no edge exists between the vertices.
+     *
+     * @param graph The graph represented as an adjacency matrix.
+     * @param source The source vertex.
+     * @return An array where the value at each index {@code i} represents the shortest distance from the source vertex to vertex {@code i}.
+     * @throws IllegalArgumentException if the source vertex is out of range.
+     */
+    public int[] run(int[][] graph, int source) {
+        if (source < 0 || source >= vertexCount) {
+            throw new IllegalArgumentException("Incorrect source");
+        }
+
+        int[] distances = new int[vertexCount];
+        boolean[] processed = new boolean[vertexCount];
+
+        Arrays.fill(distances, Integer.MAX_VALUE);
+        Arrays.fill(processed, false);
+        distances[source] = 0;
+
+        for (int count = 0; count < vertexCount - 1; count++) {
+            int u = getMinDistanceVertex(distances, processed);
+            processed[u] = true;
+
+            for (int v = 0; v < vertexCount; v++) {
+                if (!processed[v] && graph[u][v] != 0 && distances[u] != Integer.MAX_VALUE && distances[u] + graph[u][v] < distances[v]) {
+                    distances[v] = distances[u] + graph[u][v];
+                }
+            }
+        }
+
+        printDistances(distances);
+        return distances;
+    }
+
+    /**
+     * Finds the vertex with the minimum distance value from the set of vertices that have not yet been processed.
+     *
+     * @param distances The array of current shortest distances from the source vertex.
+     * @param processed The array indicating whether each vertex has been processed.
+     * @return The index of the vertex with the minimum distance value.
+     */
+    private int getMinDistanceVertex(int[] distances, boolean[] processed) {
+        int min = Integer.MAX_VALUE;
+        int minIndex = -1;
+
+        for (int v = 0; v < vertexCount; v++) {
+            if (!processed[v] && distances[v] <= min) {
+                min = distances[v];
+                minIndex = v;
+            }
+        }
+
+        return minIndex;
+    }
+
+    /**
+     * Prints the shortest distances from the source vertex to all other vertices.
+     *
+     * @param distances The array of shortest distances.
+     */
+    private void printDistances(int[] distances) {
+        System.out.println("Vertex \t Distance");
+        for (int i = 0; i < vertexCount; i++) {
+            System.out.println(i + " \t " + distances[i]);
+        }
+    }
+}

src/main/java/com/thealgorithms/datastructures/graphs/FloydWarshall.java

@@ -4,31 +4,31 @@ import java.util.Scanner;
 
 public class FloydWarshall {
 
-    private int[][] DistanceMatrix;
+    private int[][] distanceMatrix;
     private int numberofvertices; // number of vertices in the graph
     public static final int INFINITY = 999;
 
     public FloydWarshall(int numberofvertices) {
-        DistanceMatrix = new int[numberofvertices + 1][numberofvertices + 1]; // stores the value of distance from all the possible path form the source
+        distanceMatrix = new int[numberofvertices + 1][numberofvertices + 1]; // stores the value of distance from all the possible path form the source
         // vertex to destination vertex
         // The matrix is initialized with 0's by default
         this.numberofvertices = numberofvertices;
     }
 
-    public void floydwarshall(int[][] AdjacencyMatrix) { // calculates all the distances from source to destination vertex
+    public void floydwarshall(int[][] adjacencyMatrix) { // calculates all the distances from source to destination vertex
         for (int source = 1; source <= numberofvertices; source++) {
             for (int destination = 1; destination <= numberofvertices; destination++) {
-                DistanceMatrix[source][destination] = AdjacencyMatrix[source][destination];
+                distanceMatrix[source][destination] = adjacencyMatrix[source][destination];
             }
         }
         for (int intermediate = 1; intermediate <= numberofvertices; intermediate++) {
             for (int source = 1; source <= numberofvertices; source++) {
                 for (int destination = 1; destination <= numberofvertices; destination++) {
-                    if (DistanceMatrix[source][intermediate] + DistanceMatrix[intermediate][destination] < DistanceMatrix[source][destination]) { // calculated distance it get replaced as
+                    if (distanceMatrix[source][intermediate] + distanceMatrix[intermediate][destination] < distanceMatrix[source][destination]) { // calculated distance it get replaced as
                                                                                                                                                   // new shortest distance // if the new
                                                                                                                                                   // distance calculated is less then the
                                                                                                                                                   // earlier shortest
-                        DistanceMatrix[source][destination] = DistanceMatrix[source][intermediate] + DistanceMatrix[intermediate][destination];
+                        distanceMatrix[source][destination] = distanceMatrix[source][intermediate] + distanceMatrix[intermediate][destination];
                     }
                 }
             }
@@ -40,7 +40,7 @@ public class FloydWarshall {
         for (int source = 1; source <= numberofvertices; source++) {
             System.out.print(source + "\t");
             for (int destination = 1; destination <= numberofvertices; destination++) {
-                System.out.print(DistanceMatrix[source][destination] + "\t");
+                System.out.print(distanceMatrix[source][destination] + "\t");
             }
             System.out.println();
         }

src/main/java/com/thealgorithms/datastructures/graphs/FordFulkerson.java

@@ -0,0 +1,57 @@
+package com.thealgorithms.datastructures.graphs;
+
+import java.util.LinkedList;
+import java.util.Queue;
+
+public final class FordFulkerson {
+    private static final int INF = Integer.MAX_VALUE;
+
+    private FordFulkerson() {
+    }
+
+    public static int networkFlow(int vertexCount, int[][] capacity, int[][] flow, int source, int sink) {
+        int totalFlow = 0;
+
+        while (true) {
+            int[] parent = new int[vertexCount];
+            boolean[] visited = new boolean[vertexCount];
+            Queue<Integer> queue = new LinkedList<>();
+
+            queue.add(source);
+            visited[source] = true;
+            parent[source] = -1;
+
+            while (!queue.isEmpty() && !visited[sink]) {
+                int current = queue.poll();
+
+                for (int next = 0; next < vertexCount; next++) {
+                    if (!visited[next] && capacity[current][next] - flow[current][next] > 0) {
+                        queue.add(next);
+                        visited[next] = true;
+                        parent[next] = current;
+                    }
+                }
+            }
+
+            if (!visited[sink]) {
+                break; // No more augmenting paths
+            }
+
+            int pathFlow = INF;
+            for (int v = sink; v != source; v = parent[v]) {
+                int u = parent[v];
+                pathFlow = Math.min(pathFlow, capacity[u][v] - flow[u][v]);
+            }
+
+            for (int v = sink; v != source; v = parent[v]) {
+                int u = parent[v];
+                flow[u][v] += pathFlow;
+                flow[v][u] -= pathFlow;
+            }
+
+            totalFlow += pathFlow;
+        }
+
+        return totalFlow;
+    }
+}

src/main/java/com/thealgorithms/datastructures/graphs/Graphs.java

@@ -6,7 +6,7 @@ class AdjacencyListGraph<E extends Comparable<E>> {
 
     ArrayList<Vertex> vertices;
 
-    public AdjacencyListGraph() {
+    AdjacencyListGraph() {
         vertices = new ArrayList<>();
     }
 
@@ -15,7 +15,7 @@ class AdjacencyListGraph<E extends Comparable<E>> {
         E data;
         ArrayList<Vertex> adjacentVertices;
 
-        public Vertex(E data) {
+        Vertex(E data) {
             adjacentVertices = new ArrayList<>();
             this.data = data;
         }
@@ -75,7 +75,8 @@ class AdjacencyListGraph<E extends Comparable<E>> {
      * already did
      */
     public boolean addEdge(E from, E to) {
-        Vertex fromV = null, toV = null;
+        Vertex fromV = null;
+        Vertex toV = null;
         for (Vertex v : vertices) {
             if (from.compareTo(v.data) == 0) { // see if from vertex already exists
                 fromV = v;
@@ -120,7 +121,9 @@ class AdjacencyListGraph<E extends Comparable<E>> {
     }
 }
 
-public class Graphs {
+public final class Graphs {
+    private Graphs() {
+    }
 
     public static void main(String[] args) {
         AdjacencyListGraph<Integer> graph = new AdjacencyListGraph<>();

src/main/java/com/thealgorithms/datastructures/graphs/HamiltonianCycle.java

@@ -2,13 +2,14 @@ package com.thealgorithms.datastructures.graphs;
 
 /**
  * Java program for Hamiltonian Cycle
- * (https://en.wikipedia.org/wiki/Hamiltonian_path)
+ * <a href="https://en.wikipedia.org/wiki/Hamiltonian_path">wikipedia</a>
  *
- * @author Akshay Dubey (https://github.com/itsAkshayDubey)
+ * @author  <a href="https://github.com/itsAkshayDubey">Akshay Dubey</a>
  */
 public class HamiltonianCycle {
 
-    private int V, pathCount;
+    private int vertex;
+    private int pathCount;
     private int[] cycle;
     private int[][] graph;
 
@@ -21,8 +22,8 @@ public class HamiltonianCycle {
      *         else returns 1D array with value -1.
      */
     public int[] findHamiltonianCycle(int[][] graph) {
-        this.V = graph.length;
-        this.cycle = new int[this.V + 1];
+        this.vertex = graph.length;
+        this.cycle = new int[this.vertex + 1];
 
         // Initialize path array with -1 value
         for (int i = 0; i < this.cycle.length; i++) {
@@ -52,36 +53,36 @@ public class HamiltonianCycle {
      * @returns true if path is found false otherwise
      */
     public boolean isPathFound(int vertex) {
-        boolean isLastVertexConnectedToStart = this.graph[vertex][0] == 1 && this.pathCount == this.V;
+        boolean isLastVertexConnectedToStart = this.graph[vertex][0] == 1 && this.pathCount == this.vertex;
         if (isLastVertexConnectedToStart) {
             return true;
         }
 
-        /** all vertices selected but last vertex not linked to 0 **/
-        if (this.pathCount == this.V) {
+        /* all vertices selected but last vertex not linked to 0 **/
+        if (this.pathCount == this.vertex) {
             return false;
         }
 
-        for (int v = 0; v < this.V; v++) {
-            /** if connected **/
+        for (int v = 0; v < this.vertex; v++) {
+            /* if connected **/
             if (this.graph[vertex][v] == 1) {
-                /** add to path **/
+                /* add to path **/
                 this.cycle[this.pathCount++] = v;
 
-                /** remove connection **/
+                /* remove connection **/
                 this.graph[vertex][v] = 0;
                 this.graph[v][vertex] = 0;
 
-                /** if vertex not already selected solve recursively **/
+                /* if vertex not already selected solve recursively **/
                 if (!isPresent(v)) {
                     return isPathFound(v);
                 }
 
-                /** restore connection **/
+                /* restore connection **/
                 this.graph[vertex][v] = 1;
                 this.graph[v][vertex] = 1;
 
-                /** remove path **/
+                /* remove path **/
                 this.cycle[--this.pathCount] = -1;
             }
         }

src/main/java/com/thealgorithms/datastructures/graphs/KahnsAlgorithm.java

@@ -8,9 +8,6 @@ import java.util.Map;
 import java.util.Queue;
 import java.util.Set;
 
-/**
- * An algorithm that sorts a graph in toplogical order.
- */
 /**
  * A class that represents the adjaceny list of a graph
  */
@@ -54,19 +51,6 @@ class AdjacencyList<E extends Comparable<E>> {
     Set<E> getVertices() {
         return adj.keySet();
     }
-
-    /**
-     * Prints the adjacency list
-     */
-    void printGraph() {
-        for (E vertex : adj.keySet()) {
-            System.out.print(vertex + " : ");
-            for (E adjacent : adj.get(vertex)) {
-                System.out.print(adjacent + " ");
-            }
-            System.out.println();
-        }
-    }
 }
 
 class TopologicalSort<E extends Comparable<E>> {
@@ -104,9 +88,9 @@ class TopologicalSort<E extends Comparable<E>> {
         calculateInDegree();
         Queue<E> q = new LinkedList<E>();
 
-        for (E vertex : inDegree.keySet()) {
-            if (inDegree.get(vertex) == 0) {
-                q.add(vertex);
+        for (final var entry : inDegree.entrySet()) {
+            if (entry.getValue() == 0) {
+                q.add(entry.getKey());
             }
         }
 
@@ -130,7 +114,9 @@ class TopologicalSort<E extends Comparable<E>> {
 /**
  * A driver class that sorts a given graph in topological order.
  */
-public class KahnsAlgorithm {
+public final class KahnsAlgorithm {
+    private KahnsAlgorithm() {
+    }
 
     public static void main(String[] args) {
         // Graph definition and initialization

src/main/java/com/thealgorithms/datastructures/graphs/Kosaraju.java

@@ -6,53 +6,50 @@ import java.util.Stack;
 
 /**
  * Java program that implements Kosaraju Algorithm.
- * @author Shivanagouda S A (https://github.com/shivu2002a)
- *
- */
-
-/**
+ * @author <a href="https://github.com/shivu2002a">Shivanagouda S A</a>
+ * <p>
  * Kosaraju algorithm is a linear time algorithm to find the strongly connected components of a
-   directed graph, which, from here onwards will be referred by SCC. It leverages the fact that the
- transpose graph (same graph with all the edges reversed) has exactly the same SCCs as the original
- graph.
+directed graph, which, from here onwards will be referred by SCC. It leverages the fact that the
+transpose graph (same graph with all the edges reversed) has exactly the same SCCs as the original
+graph.
 
  * A graph is said to be strongly connected if every vertex is reachable from every other vertex.
-   The SCCs of a directed graph form a partition into subgraphs that are themselves strongly
- connected. Single node is always a SCC.
+The SCCs of a directed graph form a partition into subgraphs that are themselves strongly
+connected. Single node is always a SCC.
 
  * Example:
 
-    0 <--- 2 -------> 3 -------- > 4 ---- > 7
-    |     ^                      | ^       ^
-    |    /                       |  \     /
-    |   /                        |   \   /
-    v  /                         v    \ /
-    1                            5 --> 6
+0 <--- 2 -------> 3 -------- > 4 ---- > 7
+|     ^                      | ^       ^
+|    /                       |  \     /
+|   /                        |   \   /
+v  /                         v    \ /
+1                            5 --> 6
 
-    For the above graph, the SCC list goes as follows:
-    0, 1, 2
-    3
-    4, 5, 6
-    7
+For the above graph, the SCC list goes as follows:
+0, 1, 2
+3
+4, 5, 6
+7
 
-    We can also see that order of the nodes in an SCC doesn't matter since they are in cycle.
+We can also see that order of the nodes in an SCC doesn't matter since they are in cycle.
 
- {@summary}
+{@summary}
  * Kosaraju Algorithm:
-    1. Perform DFS traversal of the graph. Push node to stack before returning. This gives edges
- sorted by lowest finish time.
-    2. Find the transpose graph by reversing the edges.
-    3. Pop nodes one by one from the stack and again to DFS on the modified graph.
+1. Perform DFS traversal of the graph. Push node to stack before returning. This gives edges
+sorted by lowest finish time.
+2. Find the transpose graph by reversing the edges.
+3. Pop nodes one by one from the stack and again to DFS on the modified graph.
 
-    The transpose graph of the above graph:
-     0 ---> 2 <------- 3 <------- 4 <------ 7
-    ^     /                      ^ \       /
-    |    /                       |  \     /
-    |   /                        |   \   /
-    |  v                         |    v v
-    1                            5 <--- 6
+The transpose graph of the above graph:
+0 ---> 2 <------- 3 <------- 4 <------ 7
+^     /                      ^ \       /
+|    /                       |  \     /
+|   /                        |   \   /
+|  v                         |    v v
+1                            5 <--- 6
 
-    We can observe that this graph has the same SCC as that of original graph.
+We can observe that this graph has the same SCC as that of original graph.
 
  */
 
@@ -127,7 +124,9 @@ public class Kosaraju {
     private void dfs(int node, int[] vis, List<List<Integer>> list) {
         vis[node] = 1;
         for (Integer neighbour : list.get(node)) {
-            if (vis[neighbour] == 0) dfs(neighbour, vis, list);
+            if (vis[neighbour] == 0) {
+                dfs(neighbour, vis, list);
+            }
         }
         stack.push(node);
     }
@@ -136,7 +135,9 @@ public class Kosaraju {
     private void dfs2(int node, int[] vis, List<List<Integer>> list) {
         vis[node] = 1;
         for (Integer neighbour : list.get(node)) {
-            if (vis[neighbour] == 0) dfs2(neighbour, vis, list);
+            if (vis[neighbour] == 0) {
+                dfs2(neighbour, vis, list);
+            }
         }
         scc.add(node);
     }

src/main/java/com/thealgorithms/datastructures/graphs/Kruskal.java

@@ -23,7 +23,7 @@ public class Kruskal {
         private int to;
         private int weight;
 
-        public Edge(int from, int to, int weight) {
+        Edge(int from, int to, int weight) {
             this.from = from;
             this.to = to;
             this.weight = weight;

src/main/java/com/thealgorithms/datastructures/graphs/MatrixGraphs.java

@@ -12,7 +12,9 @@ import java.util.Queue;
  *
  * @author Unknown
  */
-public class MatrixGraphs {
+public final class MatrixGraphs {
+    private MatrixGraphs() {
+    }
 
     public static void main(String[] args) {
         AdjacencyMatrixGraph graph = new AdjacencyMatrixGraph(10);
@@ -46,17 +48,17 @@ class AdjacencyMatrixGraph {
     /**
      * The number of vertices in the graph
      */
-    private int _numberOfVertices;
+    private int vertexCount;
 
     /**
      * The number of edges in the graph
      */
-    private int _numberOfEdges;
+    private int edgeCount;
 
     /**
      * The adjacency matrix for the graph
      */
-    private int[][] _adjacency;
+    private int[][] adjMatrix;
 
     /**
      * Static variables to define whether or not an edge exists in the adjacency
@@ -68,7 +70,7 @@ class AdjacencyMatrixGraph {
     /**
      * Constructor
      */
-    public AdjacencyMatrixGraph(int givenNumberOfVertices) {
+    AdjacencyMatrixGraph(int givenNumberOfVertices) {
         this.setNumberOfVertices(givenNumberOfVertices);
         this.setNumberOfEdges(0);
         this.setAdjacency(new int[givenNumberOfVertices][givenNumberOfVertices]);
@@ -85,16 +87,16 @@ class AdjacencyMatrixGraph {
      * @param newNumberOfVertices the new number of vertices
      */
     private void setNumberOfVertices(int newNumberOfVertices) {
-        this._numberOfVertices = newNumberOfVertices;
+        this.vertexCount = newNumberOfVertices;
     }
 
     /**
-     * Getter for `this._numberOfVertices`
+     * Getter for `this.vertexCount`
      *
      * @return the number of vertices in the graph
      */
     public int numberOfVertices() {
-        return this._numberOfVertices;
+        return this.vertexCount;
     }
 
     /**
@@ -104,16 +106,16 @@ class AdjacencyMatrixGraph {
      *
      */
     private void setNumberOfEdges(int newNumberOfEdges) {
-        this._numberOfEdges = newNumberOfEdges;
+        this.edgeCount = newNumberOfEdges;
     }
 
     /**
-     * Getter for `this._numberOfEdges`
+     * Getter for `this.edgeCount`
      *
      * @return the number of edges
      */
     public int numberOfEdges() {
-        return this._numberOfEdges;
+        return this.edgeCount;
     }
 
     /**
@@ -122,7 +124,7 @@ class AdjacencyMatrixGraph {
      * @param newAdjacency the new adjaceny matrix
      */
     private void setAdjacency(int[][] newAdjacency) {
-        this._adjacency = newAdjacency;
+        this.adjMatrix = newAdjacency;
     }
 
     /**
@@ -131,7 +133,7 @@ class AdjacencyMatrixGraph {
      * @return the adjacency matrix
      */
     private int[][] adjacency() {
-        return this._adjacency;
+        return this.adjMatrix;
     }
 
     /**
@@ -220,12 +222,12 @@ class AdjacencyMatrixGraph {
      */
     public List<Integer> depthFirstOrder(int startVertex) {
         // If the startVertex is invalid, return an empty list
-        if (startVertex >= _numberOfVertices || startVertex < 0) {
+        if (startVertex >= vertexCount || startVertex < 0) {
             return new ArrayList<Integer>();
         }
 
         // Create an array to track the visited vertices
-        boolean[] visited = new boolean[_numberOfVertices];
+        boolean[] visited = new boolean[vertexCount];
 
         // Create a list to keep track of the order of our traversal
         ArrayList<Integer> orderList = new ArrayList<Integer>();
@@ -257,7 +259,7 @@ class AdjacencyMatrixGraph {
         orderList.add(currentVertex);
 
         // Get the adjacency array for this vertex
-        int[] adjacent = _adjacency[currentVertex];
+        int[] adjacent = adjMatrix[currentVertex];
         for (int i = 0; i < adjacent.length; i++) { // we are considering exploring, recurse on it // If an edge exists between the
                                                     // currentVertex and the vertex
             if (adjacent[i] == AdjacencyMatrixGraph.EDGE_EXIST) {
@@ -275,12 +277,12 @@ class AdjacencyMatrixGraph {
      */
     public List<Integer> breadthFirstOrder(int startVertex) {
         // If the specified startVertex is invalid, return an empty list
-        if (startVertex >= _numberOfVertices || startVertex < 0) {
+        if (startVertex >= vertexCount || startVertex < 0) {
             return new ArrayList<Integer>();
         }
 
         // Create an array to keep track of the visited vertices
-        boolean[] visited = new boolean[_numberOfVertices];
+        boolean[] visited = new boolean[vertexCount];
 
         // Create a list to keep track of the ordered vertices
         ArrayList<Integer> orderList = new ArrayList<Integer>();
@@ -307,7 +309,7 @@ class AdjacencyMatrixGraph {
 
             // Get the adjacency array for the currentVertex and
             // check each node
-            int[] adjacent = _adjacency[currentVertex];
+            int[] adjacent = adjMatrix[currentVertex];
             for (int vertex = 0; vertex < adjacent.length; vertex++) { // vertex we are considering exploring, we add it to the queue // If an
                                                                        // edge exists between the current vertex and the
                 if (adjacent[vertex] == AdjacencyMatrixGraph.EDGE_EXIST) {
@@ -334,7 +336,7 @@ class AdjacencyMatrixGraph {
         for (int i = 0; i < this.numberOfVertices(); i++) {
             s = s + i + " : ";
             for (int j = 0; j < this.numberOfVertices(); j++) {
-                s = s + this._adjacency[i][j] + " ";
+                s = s + this.adjMatrix[i][j] + " ";
             }
             s = s + "\n";
         }

src/main/java/com/thealgorithms/datastructures/graphs/PrimMST.java

@@ -14,16 +14,17 @@ class PrimMST {
     // value, from the set of vertices not yet included in MST
     int minKey(int[] key, Boolean[] mstSet) {
         // Initialize min value
-        int min = Integer.MAX_VALUE, min_index = -1;
+        int min = Integer.MAX_VALUE;
+        int minIndex = -1;
 
         for (int v = 0; v < V; v++) {
             if (!mstSet[v] && key[v] < min) {
                 min = key[v];
-                min_index = v;
+                minIndex = v;
             }
         }
 
-        return min_index;
+        return minIndex;
     }
 
     // A utility function to print the constructed MST stored in
@@ -50,7 +51,7 @@ class PrimMST {
         // Initialize all keys as INFINITE
         for (int i = 0; i < V; i++) {
             key[i] = Integer.MAX_VALUE;
-            mstSet[i] = false;
+            mstSet[i] = Boolean.FALSE;
         }
 
         // Always include first 1st vertex in MST.
@@ -65,7 +66,7 @@ class PrimMST {
             int u = minKey(key, mstSet);
 
             // Add the picked vertex to the MST Set
-            mstSet[u] = true;
+            mstSet[u] = Boolean.TRUE;
 
             // Update key value and parent index of the adjacent
             // vertices of the picked vertex. Consider only those

src/main/java/com/thealgorithms/datastructures/graphs/TarjansAlgorithm.java

@@ -6,61 +6,58 @@ import java.util.Stack;
 
 /**
  * Java program that implements Tarjan's Algorithm.
- * @author Shivanagouda S A (https://github.com/shivu2002a)
- *
- */
-
-/**
+ * @author <a href="https://github.com/shivu2002a">Shivanagouda S A</a>
+ * <p>
  * Tarjan's algorithm is a linear time algorithm to find the strongly connected components of a
-   directed graph, which, from here onwards will be referred as SCC.
+directed graph, which, from here onwards will be referred as SCC.
 
  * A graph is said to be strongly connected if every vertex is reachable from every other vertex.
-   The SCCs of a directed graph form a partition into subgraphs that are themselves strongly
- connected. Single node is always a SCC.
+The SCCs of a directed graph form a partition into subgraphs that are themselves strongly
+connected. Single node is always a SCC.
 
  * Example:
-    0 --------> 1 -------> 3 --------> 4
-    ^          /
-    |         /
-    |        /
-    |       /
-    |      /
-    |     /
-    |    /
-    |   /
-    |  /
-    | /
-    |V
-    2
+0 --------> 1 -------> 3 --------> 4
+^          /
+|         /
+|        /
+|       /
+|      /
+|     /
+|    /
+|   /
+|  /
+| /
+|V
+2
 
-    For the above graph, the SCC list goes as follows:
-    1, 2, 0
-    3
-    4
+For the above graph, the SCC list goes as follows:
+1, 2, 0
+3
+4
 
-    We can also see that order of the nodes in an SCC doesn't matter since they are in cycle.
+We can also see that order of the nodes in an SCC doesn't matter since they are in cycle.
 
- {@summary}
-    Tarjan's Algorithm:
-    * DFS search produces a DFS tree
-    * Strongly Connected Components form subtrees of the DFS tree.
-    * If we can find the head of these subtrees, we can get all the nodes in that subtree (including
- the head) and that will be one SCC.
-    * There is no back edge from one SCC to another (here can be cross edges, but they will not be
- used).
+{@summary}
+Tarjan's Algorithm:
+ * DFS search produces a DFS tree
+ * Strongly Connected Components form subtrees of the DFS tree.
+ * If we can find the head of these subtrees, we can get all the nodes in that subtree (including
+the head) and that will be one SCC.
+ * There is no back edge from one SCC to another (here can be cross edges, but they will not be
+used).
 
-    * Kosaraju Algorithm aims at doing the same but uses two DFS traversalse whereas Tarjan’s
- algorithm does the same in a single DFS, which leads to much lower constant factors in the latter.
+ * Kosaraju Algorithm aims at doing the same but uses two DFS traversalse whereas Tarjan’s
+algorithm does the same in a single DFS, which leads to much lower constant factors in the latter.
 
  */
 public class TarjansAlgorithm {
 
     // Timer for tracking lowtime and insertion time
-    private int Time;
+    private int time;
 
-    private List<List<Integer>> SCClist = new ArrayList<List<Integer>>();
+    private final List<List<Integer>> sccList = new ArrayList<List<Integer>>();
 
-    public List<List<Integer>> stronglyConnectedComponents(int V, List<List<Integer>> graph) {
+    public List<List<Integer>> stronglyConnectedComponents(int v, List<List<Integer>> graph) {
 
         // Initially all vertices as unvisited, insertion and low time are undefined
 
@@ -68,32 +65,34 @@ public class TarjansAlgorithm {
 
         // lowTime: indicates the earliest visited vertex (the vertex with minimum insertion time)
         // that can be reached from a subtree rooted with a particular node.
-        int[] lowTime = new int[V];
-        int[] insertionTime = new int[V];
-        for (int i = 0; i < V; i++) {
+        int[] lowTime = new int[v];
+        int[] insertionTime = new int[v];
+        for (int i = 0; i < v; i++) {
             insertionTime[i] = -1;
             lowTime[i] = -1;
         }
 
         // To check if element is present in stack
-        boolean[] isInStack = new boolean[V];
+        boolean[] isInStack = new boolean[v];
 
         // Store nodes during DFS
         Stack<Integer> st = new Stack<Integer>();
 
-        for (int i = 0; i < V; i++) {
-            if (insertionTime[i] == -1) stronglyConnCompsUtil(i, lowTime, insertionTime, isInStack, st, graph);
+        for (int i = 0; i < v; i++) {
+            if (insertionTime[i] == -1) {
+                stronglyConnCompsUtil(i, lowTime, insertionTime, isInStack, st, graph);
+            }
         }
 
-        return SCClist;
+        return sccList;
     }
 
     private void stronglyConnCompsUtil(int u, int[] lowTime, int[] insertionTime, boolean[] isInStack, Stack<Integer> st, List<List<Integer>> graph) {
 
         // Initialize insertion time and lowTime value of current node
-        insertionTime[u] = Time;
-        lowTime[u] = Time;
-        Time += 1;
+        insertionTime[u] = time;
+        lowTime[u] = time;
+        time += 1;
 
         // Push current node into stack
         isInStack[u] = true;
@@ -123,7 +122,7 @@ public class TarjansAlgorithm {
                 scc.add(w);
                 isInStack[w] = false;
             }
-            SCClist.add(scc);
+            sccList.add(scc);
         }
     }
 }

src/main/java/com/thealgorithms/datastructures/graphs/WelshPowell.java

@@ -17,7 +17,7 @@ public final class WelshPowell {
     private WelshPowell() {
     }
 
-    static class Graph {
+    static final class Graph {
         private HashSet<Integer>[] adjacencyLists;
 
         private Graph(int vertices) {

src/main/java/com/thealgorithms/datastructures/hashmap/hashing/GenericHashMapUsingArray.java

@@ -19,8 +19,8 @@ public class GenericHashMapUsingArray<K, V> {
     // 75, then adding 76th item it will double the size, copy all elements
     // & then add 76th item.
 
-    private void initBuckets(int N) {
-        buckets = new LinkedList[N];
+    private void initBuckets(int n) {
+        buckets = new LinkedList[n];
         for (int i = 0; i < buckets.length; i++) {
             buckets[i] = new LinkedList<>();
         }
@@ -47,8 +47,7 @@ public class GenericHashMapUsingArray<K, V> {
 
     // tells which bucket to go to
     private int hashFunction(K key) {
-        int hc = key.hashCode();
-        return Math.abs(hc) % buckets.length;
+        return Math.floorMod(key.hashCode(), buckets.length);
     }
 
     private void reHash() {

src/main/java/com/thealgorithms/datastructures/hashmap/hashing/GenericHashMapUsingArrayList.java

@@ -105,7 +105,7 @@ public class GenericHashMapUsingArrayList<K, V> {
         K key;
         V val;
 
-        public Node(K key, V val) {
+        Node(K key, V val) {
             this.key = key;
             this.val = val;
         }

src/main/java/com/thealgorithms/datastructures/hashmap/hashing/HashMap.java

@@ -1,142 +1,275 @@
 package com.thealgorithms.datastructures.hashmap.hashing;
 
-public class HashMap {
+/**
+ * A generic HashMap implementation that uses separate chaining with linked lists
+ * to handle collisions. The class supports basic operations such as insert, delete,
+ * and search, as well as displaying the contents of the hash map.
+ *
+ * @param <K> the type of keys maintained by this map
+ * @param <V> the type of mapped values
+ */
+public class HashMap<K, V> {
+    private final int hashSize;
+    private final LinkedList<K, V>[] buckets;
 
-    private final int hsize;
-    private final LinkedList[] buckets;
-
-    public HashMap(int hsize) {
-        buckets = new LinkedList[hsize];
-        for (int i = 0; i < hsize; i++) {
-            buckets[i] = new LinkedList();
-            // Java requires explicit initialization of each object
+    /**
+     * Constructs a HashMap with the specified hash size.
+     *
+     * @param hashSize the number of buckets in the hash map
+     */
+    @SuppressWarnings("unchecked")
+    public HashMap(int hashSize) {
+        this.hashSize = hashSize;
+        // Safe to suppress warning because we are creating an array of generic type
+        this.buckets = new LinkedList[hashSize];
+        for (int i = 0; i < hashSize; i++) {
+            buckets[i] = new LinkedList<>();
         }
-        this.hsize = hsize;
     }
 
-    public int hashing(int key) {
-        int hash = key % hsize;
-        if (hash < 0) {
-            hash += hsize;
+    /**
+     * Computes the hash code for the specified key.
+     * Null keys are hashed to bucket 0.
+     *
+     * @param key the key for which the hash code is to be computed
+     * @return the hash code corresponding to the key
+     */
+    private int computeHash(K key) {
+        if (key == null) {
+            return 0; // Use a special bucket (e.g., bucket 0) for null keys
         }
-        return hash;
+        int hash = key.hashCode() % hashSize;
+        return hash < 0 ? hash + hashSize : hash;
     }
 
-    public void insertHash(int key) {
-        int hash = hashing(key);
-        buckets[hash].insert(key);
+    /**
+     * Inserts the specified key-value pair into the hash map.
+     * If the key already exists, the value is updated.
+     *
+     * @param key   the key to be inserted
+     * @param value the value to be associated with the key
+     */
+    public void insert(K key, V value) {
+        int hash = computeHash(key);
+        buckets[hash].insert(key, value);
     }
 
-    public void deleteHash(int key) {
-        int hash = hashing(key);
-
+    /**
+     * Deletes the key-value pair associated with the specified key from the hash map.
+     *
+     * @param key the key whose key-value pair is to be deleted
+     */
+    public void delete(K key) {
+        int hash = computeHash(key);
         buckets[hash].delete(key);
     }
 
-    public void displayHashtable() {
-        for (int i = 0; i < hsize; i++) {
-            System.out.printf("Bucket %d :", i);
-            System.out.println(buckets[i].display());
+    /**
+     * Searches for the value associated with the specified key in the hash map.
+     *
+     * @param key the key whose associated value is to be returned
+     * @return the value associated with the specified key, or null if the key does not exist
+     */
+    public V search(K key) {
+        int hash = computeHash(key);
+        Node<K, V> node = buckets[hash].findKey(key);
+        return node != null ? node.getValue() : null;
+    }
+
+    /**
+     * Displays the contents of the hash map, showing each bucket and its key-value pairs.
+     */
+    public void display() {
+        for (int i = 0; i < hashSize; i++) {
+            System.out.printf("Bucket %d: %s%n", i, buckets[i].display());
         }
     }
 
-    public static class LinkedList {
+    /**
+     * A nested static class that represents a linked list used for separate chaining in the hash map.
+     *
+     * @param <K> the type of keys maintained by this linked list
+     * @param <V> the type of mapped values
+     */
+    public static class LinkedList<K, V> {
+        private Node<K, V> head;
 
-        private Node first;
-
-        public LinkedList() {
-            first = null;
-        }
-
-        public void insert(int key) {
-            if (isEmpty()) {
-                first = new Node(key);
-                return;
-            }
-
-            Node temp = findEnd(first);
-            temp.setNext(new Node(key));
-        }
-
-        private Node findEnd(Node n) {
-            while (n.getNext() != null) {
-                n = n.getNext();
-            }
-            return n;
-        }
-
-        public Node findKey(int key) {
-            if (!isEmpty()) {
-                Node temp = first;
-                if (temp.getKey() == key) return temp;
-
-                while ((temp = temp.getNext()) != null) {
-                    if (temp.getKey() == key) return temp;
+        /**
+         * Inserts the specified key-value pair into the linked list.
+         * If the linked list is empty, the pair becomes the head.
+         * Otherwise, the pair is added to the end of the list.
+         *
+         * @param key   the key to be inserted
+         * @param value the value to be associated with the key
+         */
+        public void insert(K key, V value) {
+            Node<K, V> existingNode = findKey(key);
+            if (existingNode != null) {
+                existingNode.setValue(value); // Update the value, even if it's null
+            } else {
+                if (isEmpty()) {
+                    head = new Node<>(key, value);
+                } else {
+                    Node<K, V> temp = findEnd(head);
+                    temp.setNext(new Node<>(key, value));
                 }
             }
+        }
+
+        /**
+         * Finds the last node in the linked list.
+         *
+         * @param node the starting node
+         * @return the last node in the linked list
+         */
+        private Node<K, V> findEnd(Node<K, V> node) {
+            while (node.getNext() != null) {
+                node = node.getNext();
+            }
+            return node;
+        }
+
+        /**
+         * Finds the node associated with the specified key in the linked list.
+         *
+         * @param key the key to search for
+         * @return the node associated with the specified key, or null if not found
+         */
+        public Node<K, V> findKey(K key) {
+            Node<K, V> temp = head;
+            while (temp != null) {
+                if ((key == null && temp.getKey() == null) || (temp.getKey() != null && temp.getKey().equals(key))) {
+                    return temp;
+                }
+                temp = temp.getNext();
+            }
             return null;
         }
 
-        public void delete(int key) {
-            if (!isEmpty()) {
-                if (first.getKey() == key) {
-                    Node next = first.next;
-                    first.next = null; // help GC
-                    first = next;
-                } else {
-                    delete(first, key);
+        /**
+         * Deletes the node associated with the specified key from the linked list.
+         * Handles the case where the key could be null.
+         *
+         * @param key the key whose associated node is to be deleted
+         */
+        public void delete(K key) {
+            if (isEmpty()) {
+                return;
+            }
+
+            // Handle the case where the head node has the key to delete
+            if ((key == null && head.getKey() == null) || (head.getKey() != null && head.getKey().equals(key))) {
+                head = head.getNext();
+                return;
+            }
+
+            // Traverse the list to find and delete the node
+            Node<K, V> current = head;
+            while (current.getNext() != null) {
+                if ((key == null && current.getNext().getKey() == null) || (current.getNext().getKey() != null && current.getNext().getKey().equals(key))) {
+                    current.setNext(current.getNext().getNext());
+                    return;
                 }
+                current = current.getNext();
             }
         }
 
-        private void delete(Node n, int key) {
-            if (n.getNext().getKey() == key) {
-                if (n.getNext().getNext() == null) {
-                    n.setNext(null);
-                } else {
-                    n.setNext(n.getNext().getNext());
-                }
-            } else {
-                delete(n.getNext(), key);
-            }
-        }
-
+        /**
+         * Displays the contents of the linked list as a string.
+         *
+         * @return a string representation of the linked list
+         */
         public String display() {
-            return display(first);
+            return display(head);
         }
 
-        private String display(Node n) {
-            if (n == null) {
-                return "null";
-            } else {
-                return n.getKey() + "->" + display(n.getNext());
+        /**
+         * Constructs a string representation of the linked list non-recursively.
+         *
+         * @param node the starting node
+         * @return a string representation of the linked list starting from the given node
+         */
+        private String display(Node<K, V> node) {
+            StringBuilder sb = new StringBuilder();
+            while (node != null) {
+                sb.append(node.getKey()).append("=").append(node.getValue());
+                node = node.getNext();
+                if (node != null) {
+                    sb.append(" -> ");
+                }
             }
+            return sb.toString().isEmpty() ? "null" : sb.toString();
         }
 
+        /**
+         * Checks if the linked list is empty.
+         *
+         * @return true if the linked list is empty, false otherwise
+         */
         public boolean isEmpty() {
-            return first == null;
+            return head == null;
         }
     }
 
-    public static class Node {
+    /**
+     * A nested static class representing a node in the linked list.
+     *
+     * @param <K> the type of key maintained by this node
+     * @param <V> the type of value maintained by this node
+     */
+    public static class Node<K, V> {
+        private final K key;
+        private V value;
+        private Node<K, V> next;
 
-        private Node next;
-        private final int key;
-
-        public Node(int key) {
-            next = null;
+        /**
+         * Constructs a Node with the specified key and value.
+         *
+         * @param key   the key associated with this node
+         * @param value the value associated with this node
+         */
+        public Node(K key, V value) {
             this.key = key;
+            this.value = value;
         }
 
-        public Node getNext() {
-            return next;
-        }
-
-        public int getKey() {
+        /**
+         * Gets the key associated with this node.
+         *
+         * @return the key associated with this node
+         */
+        public K getKey() {
             return key;
         }
 
-        public void setNext(Node next) {
+        /**
+         * Gets the value associated with this node.
+         *
+         * @return the value associated with this node
+         */
+        public V getValue() {
+            return value;
+        }
+
+        public void setValue(V value) { // This method allows updating the value
+            this.value = value;
+        }
+
+        /**
+         * Gets the next node in the linked list.
+         *
+         * @return the next node in the linked list
+         */
+        public Node<K, V> getNext() {
+            return next;
+        }
+
+        /**
+         * Sets the next node in the linked list.
+         *
+         * @param next the next node to be linked
+         */
+        public void setNext(Node<K, V> next) {
             this.next = next;
         }
     }