Fixed Error:(6, 8) java: class algorithm is public, should be declared in a file named algorithm.java. Inside file PrimeFactorization, the name of public class was wrong.

Conversions/DecimalToBinary.java

@@ -27,7 +27,7 @@ class DecimalToBinary {
     public static void conventionalConversion() {
         int n, b = 0, c = 0, d;
         Scanner input = new Scanner(System.in);
-        System.out.printf("Conventional conversion.\n\tEnter the decimal number: ");
+        System.out.printf("Conventional conversion.%n Enter the decimal number: ");
         n = input.nextInt();
         while (n != 0) {
             d = n % 2;
@@ -46,7 +46,7 @@ class DecimalToBinary {
     public static void bitwiseConversion() {
         int n, b = 0, c = 0, d;
         Scanner input = new Scanner(System.in);
-        System.out.printf("Bitwise conversion.\n\tEnter the decimal number: ");
+        System.out.printf("Bitwise conversion.%n Enter the decimal number: ");
         n = input.nextInt();
         while (n != 0) {
             d = (n & 1);

Conversions/OctalToHexadecimal.java

@@ -15,7 +15,7 @@ public class OctalToHexadecimal {
      * @param s The Octal Number
      * @return The Decimal number
      */
-    public static int OctToDec(String s) {
+    public static int octToDec(String s) {
         int i = 0;
         for (int j = 0; j < s.length(); j++) {
             char num = s.charAt(j);
@@ -32,7 +32,7 @@ public class OctalToHexadecimal {
      * @param d The Decimal Number
      * @return The Hexadecimal number
      */
-    public static String DecimalToHex(int d) {
+    public static String decimalToHex(int d) {
         String digits = "0123456789ABCDEF";
         if (d <= 0)
             return "0";
@@ -54,10 +54,10 @@ public class OctalToHexadecimal {
         String oct = input.next();
 
         // Pass the octal number to function and get converted deciaml form
-        int decimal = OctToDec(oct);
+        int decimal = octToDec(oct);
 
         // Pass the decimla number to function and get converted Hex form of the number
-        String hex = DecimalToHex(decimal);
+        String hex = decimalToHex(decimal);
         System.out.println("The Hexadecimal equivalant is: " + hex);
         input.close();
     }

DataStructures/DynamicArray/DynamicArray.java

@@ -41,7 +41,7 @@ public class DynamicArray<E> implements Iterable<E> {
     }
 
     public void put(final int index, E element) {
-        Objects.checkIndex(index, this.size);
+//        Objects.checkIndex(index, this.size);
 
         this.elements[index] = element;
     }
@@ -79,7 +79,7 @@ public class DynamicArray<E> implements Iterable<E> {
     }
 
     private E getElement(final int index) {
-        Objects.checkIndex(index, this.size);
+//        Objects.checkIndex(index, this.size);
         return (E) this.elements[index];
     }
 

DataStructures/Graphs/BellmanFord.java

@@ -23,7 +23,7 @@ start vertex, end vertes and weights. Vertices should be labelled with a number
         * @param v End vertex
         * @param c Weight
         */
-        Edge(int a,int b,int c)
+        public Edge(int a,int b,int c)
         {
             u=a;
             v=b;

DataStructures/Graphs/MatrixGraphs.java

@@ -127,8 +127,7 @@ class AdjacencyMatrixGraph {
      * @return returns a string describing this graph
      */
     public String toString() {
-        String s = new String();
+        String s = "    ";
-        s = "    ";
         for (int i = 0; i < this.numberOfVertices(); i++) {
             s = s + String.valueOf(i) + " ";
         }

DataStructures/Heaps/HeapElement.java

@@ -117,7 +117,21 @@ public class HeapElement {
      * @return true if the keys on both elements are identical and the additional info objects
      * are identical.
      */
-    public boolean equals(HeapElement otherHeapElement) {
+    @Override
+    public boolean equals(Object o) {
+        if (o != null) {
+            if (!(o instanceof HeapElement)) return false;
+            HeapElement otherHeapElement = (HeapElement) o;
             return (this.key == otherHeapElement.key) && (this.additionalInfo.equals(otherHeapElement.additionalInfo));
         }
+        return false;
+    }
+
+    @Override
+    public int hashCode() {
+        int result = 0;
+        result = 31*result + (int) key;
+        result = 31*result + (additionalInfo != null ? additionalInfo.hashCode() : 0);
+        return result;
+    }
 }

DataStructures/Heaps/MaxHeap.java

@@ -49,9 +49,9 @@ public class MaxHeap implements Heap {
     // Toggle an element up to its right place as long as its key is lower than its parent's
     private void toggleUp(int elementIndex) {
         double key = maxHeap.get(elementIndex - 1).getKey();
-        while (getElementKey((int) Math.floor(elementIndex / 2)) < key) {
+        while (getElementKey((int) Math.floor(elementIndex / 2.0)) < key) {
-            swap(elementIndex, (int) Math.floor(elementIndex / 2));
+            swap(elementIndex, (int) Math.floor(elementIndex / 2.0));
-            elementIndex = (int) Math.floor(elementIndex / 2);
+            elementIndex = (int) Math.floor(elementIndex / 2.0);
         }
     }
 
@@ -101,7 +101,7 @@ public class MaxHeap implements Heap {
         maxHeap.set(elementIndex - 1, getElement(maxHeap.size()));
         maxHeap.remove(maxHeap.size());
         // Shall the new element be moved up...
-        if (getElementKey(elementIndex) > getElementKey((int) Math.floor(elementIndex / 2))) toggleUp(elementIndex);
+        if (getElementKey(elementIndex) > getElementKey((int) Math.floor(elementIndex / 2.0))) toggleUp(elementIndex);
             // ... or down ?
         else if (((2 * elementIndex <= maxHeap.size()) && (getElementKey(elementIndex) < getElementKey(elementIndex * 2))) ||
                 ((2 * elementIndex < maxHeap.size()) && (getElementKey(elementIndex) < getElementKey(elementIndex * 2))))

DataStructures/Heaps/MinHeap.java

@@ -44,9 +44,9 @@ public class MinHeap implements Heap {
     // Toggle an element up to its right place as long as its key is lower than its parent's
     private void toggleUp(int elementIndex) {
         double key = minHeap.get(elementIndex - 1).getKey();
-        while (getElementKey((int) Math.floor(elementIndex / 2)) > key) {
+        while (getElementKey((int) Math.floor(elementIndex / 2.0)) > key) {
-            swap(elementIndex, (int) Math.floor(elementIndex / 2));
+            swap(elementIndex, (int) Math.floor(elementIndex / 2.0));
-            elementIndex = (int) Math.floor(elementIndex / 2);
+            elementIndex = (int) Math.floor(elementIndex / 2.0);
         }
     }
 
@@ -96,7 +96,7 @@ public class MinHeap implements Heap {
         minHeap.set(elementIndex - 1, getElement(minHeap.size()));
         minHeap.remove(minHeap.size());
         // Shall the new element be moved up...
-        if (getElementKey(elementIndex) < getElementKey((int) Math.floor(elementIndex / 2))) toggleUp(elementIndex);
+        if (getElementKey(elementIndex) < getElementKey((int)Math.floor(elementIndex / 2.0))) toggleUp(elementIndex);
             // ... or down ?
         else if (((2 * elementIndex <= minHeap.size()) && (getElementKey(elementIndex) > getElementKey(elementIndex * 2))) ||
                 ((2 * elementIndex < minHeap.size()) && (getElementKey(elementIndex) > getElementKey(elementIndex * 2))))

DataStructures/Lists/CircleLinkedList.java

@@ -14,7 +14,7 @@ public class CircleLinkedList<E> {
     //For better O.O design this should be private allows for better black box design
     private int size;
     //this will point to dummy node;
-    private Node<E> head;
+    private Node<E> head =  null;
 
     //constructer for class.. here we will make a dummy node for circly linked list implementation with reduced error catching as our list will never be empty;
     public CircleLinkedList() {

DataStructures/Lists/DoublyLinkedList.java

@@ -86,9 +86,12 @@ public class DoublyLinkedList {
     public Link deleteHead() {
         Link temp = head;
         head = head.next; // oldHead <--> 2ndElement(head)
-        head.previous = null; // oldHead --> 2ndElement(head) nothing pointing at old head so will be removed
+
-        if (head == null)
+        if (head == null) {
             tail = null;
+        } else {
+            head.previous = null; // oldHead --> 2ndElement(head) nothing pointing at old head so will be removed
+        }
         return temp;
     }
 
@@ -100,10 +103,13 @@ public class DoublyLinkedList {
     public Link deleteTail() {
         Link temp = tail;
         tail = tail.previous; // 2ndLast(tail) <--> oldTail --> null
-        tail.next = null; // 2ndLast(tail) --> null
+
         if (tail == null) {
             head = null;
+        } else{
+            tail.next = null; // 2ndLast(tail) --> null
         }
+
         return temp;
     }
 

DataStructures/Stacks/NodeStack.java

@@ -74,7 +74,7 @@ public class NodeStack<Item> {
         } else {
         	newNs.setPrevious(NodeStack.head);
         	NodeStack.head.setNext(newNs);
-        	NodeStack.head = newNs;
+        	NodeStack.head.setHead(newNs);
         }
 
         NodeStack.setSize(NodeStack.getSize() + 1);
@@ -89,7 +89,7 @@ public class NodeStack<Item> {
 
     	Item item = (Item) NodeStack.head.getData();
 
-    	NodeStack.head = NodeStack.head.getPrevious();
+        NodeStack.head.setHead(NodeStack.head.getPrevious());
     	NodeStack.head.setNext(null);
 
     	NodeStack.setSize(NodeStack.getSize() - 1);

DataStructures/Trees/LevelOrderTraversal.java

@@ -15,8 +15,8 @@ public class LevelOrderTraversal {
     // Root of the Binary Tree
     Node root;
 
-    public LevelOrderTraversal() {
+    public LevelOrderTraversal( Node root) {
-        root = null;
+        this.root = root;
     }
 
     /* function to print level order traversal of tree*/

DataStructures/Trees/LevelOrderTraversalQueue.java

@@ -19,11 +19,9 @@ public class LevelOrderTraversalQueue {
         }
     }
 
-    Node root;
-
     /* Given a binary tree. Print its nodes in level order
      using array for implementing queue  */
-    void printLevelOrder() {
+    void printLevelOrder(Node root) {
         Queue<Node> queue = new LinkedList<Node>();
         queue.add(root);
         while (!queue.isEmpty()) {

DataStructures/Trees/ValidBSTOrNot.java

@@ -13,14 +13,13 @@ public class ValidBSTOrNot {
     }
 
     //Root of the Binary Tree
-    Node root;
  
     /* can give min and max value according to your code or
     can write a function to find min and max value of tree. */
 
     /* returns true if given search tree is binary
      search tree (efficient version) */
-    boolean isBST() {
+    boolean isBST(Node root) {
         return isBSTUtil(root, Integer.MIN_VALUE,
                 Integer.MAX_VALUE);
     }

DynamicProgramming/LongestIncreasingSubsequence.java

@@ -22,7 +22,7 @@ public class LongestIncreasingSubsequence {
 
     private static int upperBound(int[] ar, int l, int r, int key) {
         while (l < r - 1) {
-            int m = (l + r) / 2;
+            int m = (l + r) >>> 1;
             if (ar[m] >= key)
                 r = m;
             else

DynamicProgramming/MatrixChainMultiplication.java

@@ -25,7 +25,7 @@ public class MatrixChainMultiplication {
             count++;
         }
         for (Matrix m : mArray) {
-            System.out.format("A(%d)  =  %2d  x  %2d\n", m.count(), m.col(), m.row());
+            System.out.format("A(%d)  =  %2d  x  %2d%n", m.count(), m.col(), m.row());
         }
 
         size = mArray.size();

Maths/GCD.java

@@ -52,6 +52,6 @@ public class GCD {
 
         // call gcd function (input array)
         System.out.println(gcd(myIntArray)); // => 4
-        System.out.printf("gcd(40,24)=%d gcd(24,40)=%d\n", gcd(40, 24), gcd(24, 40)); // => 8
+        System.out.printf("gcd(40,24)=%d gcd(24,40)=%d%n", gcd(40, 24), gcd(24, 40)); // => 8
     }
 }

Others/Dijkstra.java

@@ -95,6 +95,32 @@ class Graph {
             return Integer.compare(dist, other.dist);
         }
 
+        @Override
+        public boolean equals(Object object) {
+            if (this == object) return true;
+            if (object == null || getClass() != object.getClass()) return false;
+            if (!super.equals(object)) return false;
+
+            Vertex vertex = (Vertex) object;
+
+            if (dist != vertex.dist) return false;
+            if (name != null ? !name.equals(vertex.name) : vertex.name != null) return false;
+            if (previous != null ? !previous.equals(vertex.previous) : vertex.previous != null) return false;
+            if (neighbours != null ? !neighbours.equals(vertex.neighbours) : vertex.neighbours != null) return false;
+
+            return true;
+        }
+
+        @Override
+        public int hashCode() {
+            int result = super.hashCode();
+            result = 31 * result + (name != null ? name.hashCode() : 0);
+            result = 31 * result + dist;
+            result = 31 * result + (previous != null ? previous.hashCode() : 0);
+            result = 31 * result + (neighbours != null ? neighbours.hashCode() : 0);
+            return result;
+        }
+
         @Override
         public String toString() {
             return "(" + name + ", " + dist + ")";
@@ -125,7 +151,7 @@ class Graph {
      */
     public void dijkstra(String startName) {
         if (!graph.containsKey(startName)) {
-            System.err.printf("Graph doesn't contain start vertex \"%s\"\n", startName);
+            System.err.printf("Graph doesn't contain start vertex \"%s\"%n", startName);
             return;
         }
         final Vertex source = graph.get(startName);
@@ -172,7 +198,7 @@ class Graph {
      */
     public void printPath(String endName) {
         if (!graph.containsKey(endName)) {
-            System.err.printf("Graph doesn't contain end vertex \"%s\"\n", endName);
+            System.err.printf("Graph doesn't contain end vertex \"%s\"%n", endName);
             return;
         }
 
@@ -189,4 +215,5 @@ class Graph {
             System.out.println();
         }
     }
+
 }

Others/TopKWords.java

@@ -50,6 +50,7 @@ public class TopKWords {
             } finally {
                 try {
                     // you always have to close the I/O streams
+                    if (fis != null)
                         fis.close();
                 } catch (IOException e) {
                     e.printStackTrace();

Others/TowerOfHanoi.java

@@ -12,7 +12,7 @@ class TowerOfHanoi {
 
         // Shift function is called in recursion for swapping the n-1 disc from the startPole to the intermediatePole
         shift(n - 1, startPole, endPole, intermediatePole);
-        System.out.println("\nMove \"" + n + "\" from " + startPole + " --> " + endPole); // Result Printing
+        System.out.println("%nMove \"" + n + "\" from " + startPole + " --> " + endPole); // Result Printing
         // Shift function is called in recursion for swapping the n-1 disc from the intermediatePole to the endPole
         shift(n - 1, intermediatePole, startPole, endPole);
     }

Searches/IterativeBinarySearch.java

@@ -40,7 +40,7 @@ public final class IterativeBinarySearch implements SearchAlgorithm {
         r = array.length - 1;
 
         while (l <= r) {
-            k = (l + r) / 2;
+            k = (l + r) >>> 1;
             cmp = key.compareTo(array[k]);
 
             if (cmp == 0) {

Sorts/QuickSort.java

@@ -64,7 +64,7 @@ class QuickSort implements SortAlgorithm {
      **/
 
     private static <T extends Comparable<T>> int partition(T[] array, int left, int right) {
-        int mid = (left + right) / 2;
+        int mid = (left + right) >>> 1;
         T pivot = array[mid];
 
         while (left <= right) {

ciphers/Caesar.java

@@ -125,6 +125,8 @@ public class Caesar {
             case 'D':
             case 'd':
                 System.out.println("DECODED MESSAGE IS \n" + decode(message, shift));
+            default:
+                System.out.println("default case");
         }
         input.close();
     }

ciphers/ColumnarTranspositionCipher.java

@@ -117,7 +117,7 @@ public class ColumnarTranspositionCipher {
      * order to respect the Columnar Transposition Cipher Rule.
      */
     private static int numberOfRows(String word) {
-        if ((double) word.length() / keyword.length() > word.length() / keyword.length()) {
+        if (word.length() / keyword.length() > word.length() / keyword.length()) {
             return (word.length() / keyword.length()) + 1;
         } else {
             return word.length() / keyword.length();

divideconquer/ClosestPair.java

@@ -31,6 +31,15 @@ public final class ClosestPair {
      * Minimum point length.
      */
     private static double minNum = Double.MAX_VALUE;
+
+    public static void setMinNum(double minNum) {
+        ClosestPair.minNum = minNum;
+    }
+
+    public static void setSecondCount(int secondCount) {
+        ClosestPair.secondCount = secondCount;
+    }
+
     /**
      * secondCount
      */
@@ -213,7 +222,7 @@ public final class ClosestPair {
         for (int i = 0; i < totalNum; i++) {
             double xGap = Math.abs(divideArray[divideX].x - divideArray[i].x);
             if (xGap < minValue) {
-                secondCount++; // size of the array
+                ClosestPair.setSecondCount(secondCount + 1); // size of the array
             } else {
                 if (divideArray[i].x > divideArray[divideX].x) {
                     break;
@@ -250,7 +259,7 @@ public final class ClosestPair {
                         minValue = length;
                         // Conditional for registering final coordinate
                         if (length < minNum) {
-                            minNum = length;
+                           ClosestPair.setMinNum(length);
                             point1 = firstWindow[i];
                             point2 = firstWindow[j];
                         }
@@ -260,7 +269,7 @@ public final class ClosestPair {
                 }
             }
         }
-        secondCount = 0;
+       ClosestPair.setSecondCount(0);
         return minValue;
     }
 
@@ -288,7 +297,7 @@ public final class ClosestPair {
             length = Math.sqrt(Math.pow(xGap, 2) + Math.pow(yGap, 2));
             // Conditional statement for registering final coordinate
             if (length < minNum) {
-                minNum = length;
+               ClosestPair.setMinNum(length);
 
             }
             point1 = arrayParam[0];
@@ -311,7 +320,7 @@ public final class ClosestPair {
                         minValue = length;
                         if (length < minNum) {
                             // Registering final coordinate
-                            minNum = length;
+                            ClosestPair.setMinNum(length);
                             point1 = arrayParam[i];
                             point2 = arrayParam[j];
                         }