Resolve build errors & cleanup structure (#2334)

.github/ISSUE_TEMPLATE/bug_report.md

@@ -1,10 +1,9 @@
 ---
 name: Bug report
 about: Create a report to help us improve
-title: ''
+title: ""
-labels: ''
+labels: ""
-assignees: ''
+assignees: ""
-
 ---
 
 **Describe the bug**
@@ -12,6 +11,7 @@ A clear and concise description of what the bug is.
 
 **To Reproduce**
 Steps to reproduce the behavior:
+
 1. Go to '...'
 2. Click on '....'
 3. Scroll down to '....'

.github/ISSUE_TEMPLATE/feature_request.md

@@ -1,10 +1,9 @@
 ---
 name: Feature request
 about: Suggest an idea for this project
-title: ''
+title: ""
-labels: ''
+labels: ""
-assignees: ''
+assignees: ""
-
 ---
 
 **Is your feature request related to a problem? Please describe.**

.github/workflows/build.yml

@@ -1,20 +1,14 @@
-name: Build Project
+name: Build
-
+on: push
-on:
-  pull_request:
-  push:
-    branches:
-    - master
-
 jobs:
   build:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2
-      - name: Set up JDK 12
+      - name: Set up JDK 17
         uses: actions/setup-java@v1
         with:
-          java-version: 12
+          java-version: 17
       - run: find . -type f -name "*.java" > sources.txt
       - run: javac @sources.txt

.github/workflows/checkstyle.yml

@@ -1,29 +0,0 @@
-name: Code Formatter
-
-on:
-  push:
-    branches: [master, Development]
-    paths:
-      - "**.java"
-    
-jobs:
-  format:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@master
-
-      - name: Set up JDK 12
-        uses: actions/setup-java@v1
-        with:
-          java-version: 12
-      - run: wget https://github.com/google/google-java-format/releases/download/google-java-format-1.9/google-java-format-1.9-all-deps.jar -O formatter.jar
-      - run: java -jar formatter.jar --replace --set-exit-if-changed $(find . -type f -name "*.java")
-      - name: Commit Format changes
-        if: failure()
-        run: |
-          git diff
-          git config --global user.name github-actions
-          git config --global user.email '${GITHUB_ACTOR}@users.noreply.github.com'
-          git remote set-url origin https://x-access-token:${{ secrets.GITHUB_TOKEN }}@github.com/$GITHUB_REPOSITORY
-          git commit -am "Formatted with Google Java Formatter" || true
-          git push --force origin HEAD:$GITHUB_REF || true

.github/workflows/prettify.yml

@@ -1,16 +1,8 @@
-name: Prettier
+name: Prettify
-
+on: push
-on:
-  pull_request:
-  push:
-    branches:
-    - master
-    - Development
-
 jobs:
   prettier:
     runs-on: ubuntu-latest
-
     steps:
     - name: Checkout
       uses: actions/checkout@v2
@@ -20,7 +12,7 @@ jobs:
     - name: Prettify code
       uses: creyD/prettier_action@v3.3
       with:
-        prettier_options: --write **/*.{java}
+        prettier_options: --write **/*.java
-        commit_message: 'style: prettify code'
+        commit_message: 'Prettify code'
       env:
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/stale.yml

@@ -1,7 +1,7 @@
 name: 'Close stale issues and PRs'
 on:
   schedule:
-    - cron: '0 */10 * * *'
+    - cron: '0 0 * * *'
 jobs:
   stale:
     runs-on: ubuntu-latest
@@ -16,4 +16,3 @@ jobs:
           exempt-pr-labels: 'dont-close'
           days-before-stale: 30
           days-before-close: 7
-          operations-per-run: 150

.github/workflows/update_directory.yml

@@ -1,13 +1,13 @@
 # This GitHub Action updates the DIRECTORY.md file (if needed) when doing a git push
-name: update_directory_md
+name: Update Directory
-on: [push]
+on: push
 jobs:
   update_directory_md:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@master
       - uses: actions/setup-python@master
-      - name: update_directory_md
+      - name: Update Directory
         shell: python
         run: |
             import os
@@ -63,5 +63,5 @@ jobs:
           git config --global user.email '${GITHUB_ACTOR}@users.noreply.github.com'
           git remote set-url origin https://x-access-token:${{ secrets.GITHUB_TOKEN }}@github.com/$GITHUB_REPOSITORY
           git add DIRECTORY.md
-          git commit -am "updating DIRECTORY.md" ||  true
+          git commit -am "Update directory" ||  true
           git push --force origin HEAD:$GITHUB_REF || true

.travis.yml

@@ -1,10 +0,0 @@
-os: linux
-dist: focal
-language: java
-script:
-  - find . -type f -name "*.java" > sources.txt
-  - javac -Xlint:deprecation -Xlint:unchecked @sources.txt
-notifications:
-    webhooks: https://www.travisbuddy.com/
-    on_success: never
-    on_failure: always

CONTRIBUTING.md

@@ -1,5 +1,3 @@
-:+1::tada: Before guiding you through the contribution process TheAlgorithms/Java thank you for being one of us! :+1::tada:
-
 ## How to contribute?
 
 #### **Did you find a bug?**

Ciphers/AES.java

@@ -1,4 +1,4 @@
-package ciphers;
+package Ciphers;
 
 import java.math.BigInteger;
 import java.util.Scanner;
@@ -215,30 +215,26 @@ public class AES {
 
   /**
    * Subroutine of the Rijndael key expansion.
-   *
-   * @param t
-   * @param rconCounter
-   * @return
    */
   public static BigInteger scheduleCore(BigInteger t, int rconCounter) {
-    String rBytes = t.toString(16);
+    StringBuilder rBytes = new StringBuilder(t.toString(16));
 
     // Add zero padding
     while (rBytes.length() < 8) {
-      rBytes = "0" + rBytes;
+      rBytes.insert(0, "0");
     }
 
     // rotate the first 16 bits to the back
     String rotatingBytes = rBytes.substring(0, 2);
     String fixedBytes = rBytes.substring(2);
 
-    rBytes = fixedBytes + rotatingBytes;
+    rBytes = new StringBuilder(fixedBytes + rotatingBytes);
 
     // apply S-Box to all 8-Bit Substrings
     for (int i = 0; i < 4; i++) {
-      String currentByteBits = rBytes.substring(i * 2, (i + 1) * 2);
+      StringBuilder currentByteBits = new StringBuilder(rBytes.substring(i * 2, (i + 1) * 2));
 
-      int currentByte = Integer.parseInt(currentByteBits, 16);
+      int currentByte = Integer.parseInt(currentByteBits.toString(), 16);
       currentByte = SBOX[currentByte];
 
       // add the current RCON value to the first byte
@@ -246,27 +242,26 @@ public class AES {
         currentByte = currentByte ^ RCON[rconCounter];
       }
 
-      currentByteBits = Integer.toHexString(currentByte);
+      currentByteBits = new StringBuilder(Integer.toHexString(currentByte));
 
       // Add zero padding
 
       while (currentByteBits.length() < 2) {
-        currentByteBits = '0' + currentByteBits;
+        currentByteBits.insert(0, '0');
       }
 
       // replace bytes in original string
-      rBytes = rBytes.substring(0, i * 2) + currentByteBits + rBytes.substring((i + 1) * 2);
+      rBytes = new StringBuilder(rBytes.substring(0, i * 2) + currentByteBits + rBytes.substring((i + 1) * 2));
     }
 
     // t = new BigInteger(rBytes, 16);
     // return t;
-    return new BigInteger(rBytes, 16);
+    return new BigInteger(rBytes.toString(), 16);
   }
 
   /**
    * Returns an array of 10 + 1 round keys that are calculated by using Rijndael key schedule
    *
-   * @param initialKey
    * @return array of 10 + 1 round keys
    */
   public static BigInteger[] keyExpansion(BigInteger initialKey) {
@@ -332,11 +327,11 @@ public class AES {
   public static int[] splitBlockIntoCells(BigInteger block) {
 
     int[] cells = new int[16];
-    String blockBits = block.toString(2);
+    StringBuilder blockBits = new StringBuilder(block.toString(2));
 
     // Append leading 0 for full "128-bit" string
     while (blockBits.length() < 128) {
-      blockBits = '0' + blockBits;
+      blockBits.insert(0, '0');
     }
 
     // split 128 to 8 bit cells
@@ -356,24 +351,22 @@ public class AES {
    */
   public static BigInteger mergeCellsIntoBlock(int[] cells) {
 
-    String blockBits = "";
+    StringBuilder blockBits = new StringBuilder();
     for (int i = 0; i < 16; i++) {
-      String cellBits = Integer.toBinaryString(cells[i]);
+      StringBuilder cellBits = new StringBuilder(Integer.toBinaryString(cells[i]));
 
       // Append leading 0 for full "8-bit" strings
       while (cellBits.length() < 8) {
-        cellBits = '0' + cellBits;
+        cellBits.insert(0, '0');
       }
 
-      blockBits += cellBits;
+      blockBits.append(cellBits);
     }
 
-    return new BigInteger(blockBits, 2);
+    return new BigInteger(blockBits.toString(), 2);
   }
 
   /**
-   * @param ciphertext
-   * @param key
    * @return ciphertext XOR key
    */
   public static BigInteger addRoundKey(BigInteger ciphertext, BigInteger key) {
@@ -383,7 +376,6 @@ public class AES {
   /**
    * substitutes 8-Bit long substrings of the input using the S-Box and returns the result.
    *
-   * @param ciphertext
    * @return subtraction Output
    */
   public static BigInteger subBytes(BigInteger ciphertext) {
@@ -401,7 +393,6 @@ public class AES {
    * substitutes 8-Bit long substrings of the input using the inverse S-Box for decryption and
    * returns the result.
    *
-   * @param ciphertext
    * @return subtraction Output
    */
   public static BigInteger subBytesDec(BigInteger ciphertext) {
@@ -417,8 +408,6 @@ public class AES {
 
   /**
    * Cell permutation step. Shifts cells within the rows of the input and returns the result.
-   *
-   * @param ciphertext
    */
   public static BigInteger shiftRows(BigInteger ciphertext) {
     int[] cells = splitBlockIntoCells(ciphertext);
@@ -454,8 +443,6 @@ public class AES {
   /**
    * Cell permutation step for decryption . Shifts cells within the rows of the input and returns
    * the result.
-   *
-   * @param ciphertext
    */
   public static BigInteger shiftRowsDec(BigInteger ciphertext) {
     int[] cells = splitBlockIntoCells(ciphertext);
@@ -490,8 +477,6 @@ public class AES {
 
   /**
    * Applies the Rijndael MixColumns to the input and returns the result.
-   *
-   * @param ciphertext
    */
   public static BigInteger mixColumns(BigInteger ciphertext) {
 
@@ -511,8 +496,6 @@ public class AES {
 
   /**
    * Applies the inverse Rijndael MixColumns for decryption to the input and returns the result.
-   *
-   * @param ciphertext
    */
   public static BigInteger mixColumnsDec(BigInteger ciphertext) {
 
@@ -563,7 +546,6 @@ public class AES {
    * Decrypts the ciphertext with the key and returns the result
    *
    * @param cipherText The Encrypted text which we want to decrypt
-   * @param key
    * @return decryptedText
    */
   public static BigInteger decrypt(BigInteger cipherText, BigInteger key) {
@@ -596,8 +578,7 @@ public class AES {
       char choice = input.nextLine().charAt(0);
       String in;
       switch (choice) {
-        case 'E':
+        case 'E', 'e' -> {
-        case 'e':
           System.out.println("Choose a plaintext block (128-Bit Integer in base 16):");
           in = input.nextLine();
           BigInteger plaintext = new BigInteger(in, 16);
@@ -605,10 +586,9 @@ 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));
-          break;
+        }
-        case 'D':
+        case 'D', 'd' -> {
-        case 'd':
           System.out.println("Enter your ciphertext block (128-Bit Integer in base 16):");
           in = input.nextLine();
           BigInteger ciphertext = new BigInteger(in, 16);
@@ -616,10 +596,9 @@ 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));
-          break;
+        }
-        default:
+        default -> System.out.println("** End **");
-          System.out.println("** End **");
       }
     }
   }

Ciphers/AESEncryption.java

@@ -1,4 +1,4 @@
-package ciphers;
+package Ciphers;
 
 import java.security.InvalidKeyException;
 import java.security.NoSuchAlgorithmException;
@@ -42,15 +42,12 @@ public class AESEncryption {
   public static SecretKey getSecretEncryptionKey() throws NoSuchAlgorithmException {
     KeyGenerator aesKeyGenerator = KeyGenerator.getInstance("AES");
     aesKeyGenerator.init(128); // The AES key size in number of bits
-    SecretKey secKey = aesKeyGenerator.generateKey();
+    return aesKeyGenerator.generateKey();
-    return secKey;
   }
 
   /**
    * Encrypts plainText in AES using the secret key
    *
-   * @param plainText
-   * @param secKey
    * @return byteCipherText (The encrypted text)
    * @throws NoSuchPaddingException (from Cipher)
    * @throws NoSuchAlgorithmException (from Cipher)
@@ -64,21 +61,13 @@ public class AESEncryption {
     // AES defaults to AES/ECB/PKCS5Padding in Java 7
     Cipher aesCipher = Cipher.getInstance("AES");
     aesCipher.init(Cipher.ENCRYPT_MODE, secKey);
-    byte[] byteCipherText = aesCipher.doFinal(plainText.getBytes());
+    return aesCipher.doFinal(plainText.getBytes());
-    return byteCipherText;
   }
 
   /**
    * Decrypts encrypted byte array using the key used for encryption.
    *
-   * @param byteCipherText
-   * @param secKey
    * @return plainText
-   * @throws NoSuchPaddingException
-   * @throws NoSuchAlgorithmException
-   * @throws InvalidKeyException
-   * @throws BadPaddingException
-   * @throws IllegalBlockSizeException
    */
   public static String decryptText(byte[] byteCipherText, SecretKey secKey)
       throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException,
@@ -92,10 +81,8 @@ public class AESEncryption {
 
   /**
    * Convert a binary byte array into readable hex form Old library is deprecated on OpenJdk 11 and
-   * this is faster regarding other solution is using StringBuilder Credit {@link
+   * this is faster regarding other solution is using StringBuilder
-   * https://stackoverflow.com/questions/9655181/how-to-convert-a-byte-array-to-a-hex-string-in-java/9855338#9855338}
    *
-   * @param hash (in binary)
    * @return hexHash
    */
   public static String bytesToHex(byte[] bytes) {

Ciphers/Caesar.java

@@ -1,4 +1,4 @@
-package ciphers;
+package Ciphers;
 
 import java.util.Scanner;
 
@@ -14,12 +14,10 @@ public class Caesar {
   /**
    * Encrypt text by shifting every Latin char by add number shift for ASCII Example : A + 1 -> B
    *
-   * @param message
-   * @param shift
    * @return Encrypted message
    */
   public static String encode(String message, int shift) {
-    String encoded = "";
+    StringBuilder encoded = new StringBuilder();
 
     shift %= 26;
 
@@ -33,29 +31,27 @@ public class Caesar {
       if (IsCapitalLatinLetter(current)) {
 
         current += shift;
-        encoded += (char) (current > 'Z' ? current - 26 : current); // 26 = number of latin letters
+        encoded.append((char) (current > 'Z' ? current - 26 : current)); // 26 = number of latin letters
 
       } else if (IsSmallLatinLetter(current)) {
 
         current += shift;
-        encoded += (char) (current > 'z' ? current - 26 : current); // 26 = number of latin letters
+        encoded.append((char) (current > 'z' ? current - 26 : current)); // 26 = number of latin letters
 
       } else {
-        encoded += current;
+        encoded.append(current);
       }
     }
-    return encoded;
+    return encoded.toString();
   }
 
   /**
    * Decrypt message by shifting back every Latin char to previous the ASCII Example : B - 1 -> A
    *
-   * @param encryptedMessage
-   * @param shift
    * @return message
    */
   public static String decode(String encryptedMessage, int shift) {
-    String decoded = "";
+    StringBuilder decoded = new StringBuilder();
 
     shift %= 26;
 
@@ -65,22 +61,21 @@ public class Caesar {
       if (IsCapitalLatinLetter(current)) {
 
         current -= shift;
-        decoded += (char) (current < 'A' ? current + 26 : current); // 26 = number of latin letters
+        decoded.append((char) (current < 'A' ? current + 26 : current)); // 26 = number of latin letters
 
       } else if (IsSmallLatinLetter(current)) {
 
         current -= shift;
-        decoded += (char) (current < 'a' ? current + 26 : current); // 26 = number of latin letters
+        decoded.append((char) (current < 'a' ? current + 26 : current)); // 26 = number of latin letters
 
       } else {
-        decoded += current;
+        decoded.append(current);
       }
     }
-    return decoded;
+    return decoded.toString();
   }
 
   /**
-   * @param c
    * @return true if character is capital Latin letter or false for others
    */
   private static boolean IsCapitalLatinLetter(char c) {
@@ -88,7 +83,6 @@ public class Caesar {
   }
 
   /**
-   * @param c
    * @return true if character is small Latin letter or false for others
    */
   private static boolean IsSmallLatinLetter(char c) {

Ciphers/ColumnarTranspositionCipher.java

@@ -1,4 +1,6 @@
-package ciphers;
+package Ciphers;
+
+import java.util.Objects;
 
 /**
  * Columnar Transposition Cipher Encryption and Decryption.
@@ -27,13 +29,13 @@ public class ColumnarTranspositionCipher {
     abecedariumBuilder(500);
     table = tableBuilder(word);
     Object[][] sortedTable = sortTable(table);
-    String wordEncrypted = "";
+    StringBuilder wordEncrypted = new StringBuilder();
     for (int i = 0; i < sortedTable[i].length; i++) {
       for (int j = 1; j < sortedTable.length; j++) {
-        wordEncrypted += sortedTable[j][i];
+        wordEncrypted.append(sortedTable[j][i]);
       }
     }
-    return wordEncrypted;
+    return wordEncrypted.toString();
   }
 
   /**
@@ -46,20 +48,16 @@ public class ColumnarTranspositionCipher {
    */
   public static String encrpyter(String word, String keyword, String abecedarium) {
     ColumnarTranspositionCipher.keyword = keyword;
-    if (abecedarium != null) {
+    ColumnarTranspositionCipher.abecedarium = Objects.requireNonNullElse(abecedarium, ABECEDARIUM);
-      ColumnarTranspositionCipher.abecedarium = abecedarium;
-    } else {
-      ColumnarTranspositionCipher.abecedarium = ABECEDARIUM;
-    }
     table = tableBuilder(word);
     Object[][] sortedTable = sortTable(table);
-    String wordEncrypted = "";
+    StringBuilder wordEncrypted = new StringBuilder();
     for (int i = 0; i < sortedTable[0].length; i++) {
       for (int j = 1; j < sortedTable.length; j++) {
-        wordEncrypted += sortedTable[j][i];
+        wordEncrypted.append(sortedTable[j][i]);
       }
     }
-    return wordEncrypted;
+    return wordEncrypted.toString();
   }
 
   /**
@@ -68,13 +66,13 @@ public class ColumnarTranspositionCipher {
    * @return a String decrypted with the word encrypted by the Columnar Transposition Cipher Rule
    */
   public static String decrypter() {
-    String wordDecrypted = "";
+    StringBuilder wordDecrypted = new StringBuilder();
     for (int i = 1; i < table.length; i++) {
       for (Object item : table[i]) {
-        wordDecrypted += item;
+        wordDecrypted.append(item);
       }
     }
-    return wordDecrypted.replaceAll(ENCRYPTION_FIELD, "");
+    return wordDecrypted.toString().replaceAll(ENCRYPTION_FIELD, "");
   }
 
   /**
@@ -127,7 +125,6 @@ public class ColumnarTranspositionCipher {
   }
 
   /**
-   * @param table
    * @return tableSorted
    */
   private static Object[][] sortTable(Object[][] table) {
@@ -147,9 +144,6 @@ public class ColumnarTranspositionCipher {
   }
 
   /**
-   * @param table
-   * @param rows
-   * @param column
    * @return columnArray
    */
   private static Object[] getColumn(Object[][] table, int rows, int column) {
@@ -160,12 +154,6 @@ public class ColumnarTranspositionCipher {
     return columnArray;
   }
 
-  /**
-   * @param table
-   * @param firstColumnIndex
-   * @param secondColumnIndex
-   * @param columnToSwitch
-   */
   private static void switchColumns(
       Object[][] table, int firstColumnIndex, int secondColumnIndex, Object[] columnToSwitch) {
     for (int i = 0; i < table.length; i++) {
@@ -180,10 +168,11 @@ public class ColumnarTranspositionCipher {
    * @param value Number of characters being used based on the ASCII Table
    */
   private static void abecedariumBuilder(int value) {
-    abecedarium = "";
+    StringBuilder t = new StringBuilder();
     for (int i = 0; i < value; i++) {
-      abecedarium += (char) i;
+      t.append((char) i);
     }
+    abecedarium = t.toString();
   }
 
   private static void showTable() {

Ciphers/RSA.java

@@ -1,4 +1,4 @@
-package ciphers;
+package Ciphers;
 
 import java.math.BigInteger;
 import java.security.SecureRandom;
@@ -20,13 +20,11 @@ public final class RSA {
 
   private BigInteger modulus, privateKey, publicKey;
 
-  /** @param bits */
   public RSA(int bits) {
     generateKeys(bits);
   }
 
   /**
-   * @param message
    * @return encrypted message
    */
   public synchronized String encrypt(String message) {
@@ -34,7 +32,6 @@ public final class RSA {
   }
 
   /**
-   * @param message
    * @return encrypted message as big integer
    */
   public synchronized BigInteger encrypt(BigInteger message) {
@@ -42,7 +39,6 @@ public final class RSA {
   }
 
   /**
-   * @param encryptedMessage
    * @return plain message
    */
   public synchronized String decrypt(String encryptedMessage) {
@@ -50,7 +46,6 @@ public final class RSA {
   }
 
   /**
-   * @param encryptedMessage
    * @return plain message as big integer
    */
   public synchronized BigInteger decrypt(BigInteger encryptedMessage) {
@@ -59,8 +54,6 @@ public final class RSA {
 
   /**
    * Generate a new public and private key set.
-   *
-   * @param bits
    */
   public synchronized void generateKeys(int bits) {
     SecureRandom r = new SecureRandom();

Ciphers/SimpleSubstitutionCipher.java

@@ -1,4 +1,4 @@
-package ciphers;
+package Ciphers;
 
 import java.util.*;
 
@@ -16,15 +16,13 @@ public class SimpleSubstitutionCipher {
   /**
    * Encrypt text by replacing each element with its opposite character.
    *
-   * @param message
-   * @param cipherSmall
    * @return Encrypted message
    */
   public static String encode(String message, String cipherSmall) {
-    String encoded = "";
+    StringBuilder encoded = new StringBuilder();
 
     // This map is used to encode
-    Map<Character, Character> cipherMap = new HashMap<Character, Character>();
+    Map<Character, Character> cipherMap = new HashMap<>();
 
     char beginSmallLetter = 'a';
     char beginCapitalLetter = 'A';
@@ -39,24 +37,22 @@ public class SimpleSubstitutionCipher {
     }
 
     for (int i = 0; i < message.length(); i++) {
-      if (Character.isAlphabetic(message.charAt(i))) encoded += cipherMap.get(message.charAt(i));
+      if (Character.isAlphabetic(message.charAt(i))) encoded.append(cipherMap.get(message.charAt(i)));
-      else encoded += message.charAt(i);
+      else encoded.append(message.charAt(i));
     }
 
-    return encoded;
+    return encoded.toString();
   }
 
   /**
    * Decrypt message by replacing each element with its opposite character in cipher.
    *
-   * @param encryptedMessage
-   * @param cipherSmall
    * @return message
    */
   public static String decode(String encryptedMessage, String cipherSmall) {
-    String decoded = "";
+    StringBuilder decoded = new StringBuilder();
 
-    Map<Character, Character> cipherMap = new HashMap<Character, Character>();
+    Map<Character, Character> cipherMap = new HashMap<>();
 
     char beginSmallLetter = 'a';
     char beginCapitalLetter = 'A';
@@ -71,11 +67,11 @@ public class SimpleSubstitutionCipher {
 
     for (int i = 0; i < encryptedMessage.length(); i++) {
       if (Character.isAlphabetic(encryptedMessage.charAt(i)))
-        decoded += cipherMap.get(encryptedMessage.charAt(i));
+        decoded.append(cipherMap.get(encryptedMessage.charAt(i)));
-      else decoded += encryptedMessage.charAt(i);
+      else decoded.append(encryptedMessage.charAt(i));
     }
 
-    return decoded;
+    return decoded.toString();
   }
 
   /** TODO remove main and make JUnit Testing */

Ciphers/Vigenere.java

@@ -1,4 +1,4 @@
-package ciphers;
+package Ciphers;
 
 /**
  * A Java implementation of Vigenere Cipher.

Code.html

@@ -1,68 +0,0 @@
-package Misc;
-import java.util.Scanner;
-/**
-* 
-<h1>Find the Transpose of Matrix!</h1>
-Simply take input from the user and
-* print the matrix before the transpose and after the transpose.
-* 
-<p>
-   * <b>Note:</b> Giving proper comments in your program makes it more user
-   * friendly and it is assumed as a high quality code.
-   *
-   * @author Rajat-Jain29
-   * @version 11.0.9
-   * @since 2014-03-31
-   */
-   public class matrixTranspose {
-   public static void main(String[] args) {
-   /*
-   * This is the main method
-   * 
-   * @param args Unused.
-   * 
-   * @return Nothing.
-   */
-   Scanner sc = new Scanner(System.in);
-   int i, j, row, column;
-   System.out.println("Enter the number of rows in the 2D matrix:");
-   /*
-   * Take input from user for how many rows to be print
-   */
-   row = sc.nextInt();
-   System.out.println("Enter the number of columns in the 2D matrix:");
-   /*
-   * Take input from user for how many coloumn to be print
-   */
-   column = sc.nextInt();
-   int[][] arr = new int[row][column];
-   System.out.println("Enter the elements");
-   for (i = 0; i < row; i++) {
-   for (j = 0; j < column; j++) {
-   arr[i][j] = sc.nextInt();
-   }
-   }
-   /*
-   * Print matrix before the Transpose in proper way
-   */
-   System.out.println("The matrix is:");
-   for (i = 0; i < row; i++) {
-   for (j = 0; j < column; j++) {
-   System.out.print(arr[i][j] + "\t");
-   }
-   System.out.print("\n");
-   }
-   /*
-   * Print matrix after the tranpose in proper way Transpose means Interchanging
-   * of rows wth column so we interchange the rows in next loop Thus at last
-   * matrix of transpose is obtained through user input...
-   */
-   System.out.println("The Transpose of the given matrix is:");
-   for (i = 0; i < column; i++) {
-   for (j = 0; j < row; j++) {
-   System.out.print(arr[j][i] + "\t");
-   }
-   System.out.print("\n");
-   }
-   }
-   }

DIRECTORY.md

@@ -1,12 +1,12 @@
 
-## ciphers
+## Ciphers
-  * [AES](https://github.com/TheAlgorithms/Java/blob/master/ciphers/AES.java)
+  * [AES](https://github.com/TheAlgorithms/Java/blob/master/Ciphers/AES.java)
-  * [AESEncryption](https://github.com/TheAlgorithms/Java/blob/master/ciphers/AESEncryption.java)
+  * [AESEncryption](https://github.com/TheAlgorithms/Java/blob/master/Ciphers/AESEncryption.java)
-  * [Caesar](https://github.com/TheAlgorithms/Java/blob/master/ciphers/Caesar.java)
+  * [Caesar](https://github.com/TheAlgorithms/Java/blob/master/Ciphers/Caesar.java)
-  * [ColumnarTranspositionCipher](https://github.com/TheAlgorithms/Java/blob/master/ciphers/ColumnarTranspositionCipher.java)
+  * [ColumnarTranspositionCipher](https://github.com/TheAlgorithms/Java/blob/master/Ciphers/ColumnarTranspositionCipher.java)
-  * [RSA](https://github.com/TheAlgorithms/Java/blob/master/ciphers/RSA.java)
+  * [RSA](https://github.com/TheAlgorithms/Java/blob/master/Ciphers/RSA.java)
-  * [SimpleSubstitutionCipher](https://github.com/TheAlgorithms/Java/blob/master/ciphers/SimpleSubstitutionCipher.java)
+  * [SimpleSubstitutionCipher](https://github.com/TheAlgorithms/Java/blob/master/Ciphers/SimpleSubstitutionCipher.java)
-  * [Vigenere](https://github.com/TheAlgorithms/Java/blob/master/ciphers/Vigenere.java)
+  * [Vigenere](https://github.com/TheAlgorithms/Java/blob/master/Ciphers/Vigenere.java)
 
 ## Conversions
   * [AnyBaseToAnyBase](https://github.com/TheAlgorithms/Java/blob/master/Conversions/AnyBaseToAnyBase.java)
@@ -96,9 +96,9 @@
     * [TrieImp](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/TrieImp.java)
     * [ValidBSTOrNot](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/ValidBSTOrNot.java)
 
-## divideconquer
+## DivideAndConquer
-  * [ClosestPair](https://github.com/TheAlgorithms/Java/blob/master/divideconquer/ClosestPair.java)
+  * [ClosestPair](https://github.com/TheAlgorithms/Java/blob/master/DivideAndConquer/ClosestPair.java)
-  * [SkylineAlgorithm](https://github.com/TheAlgorithms/Java/blob/master/divideconquer/SkylineAlgorithm.java)
+  * [SkylineAlgorithm](https://github.com/TheAlgorithms/Java/blob/master/DivideAndConquer/SkylineAlgorithm.java)
 
 ## DynamicProgramming
   * [BoardPath](https://github.com/TheAlgorithms/Java/blob/master/DynamicProgramming/BoardPath.java)
@@ -227,20 +227,8 @@
   * [TwoPointers](https://github.com/TheAlgorithms/Java/blob/master/Others/TwoPointers.java)
   * [WorstFit](https://github.com/TheAlgorithms/Java/blob/master/Others/WorstFit.java)
 
-## ProjectEuler
-  * [Problem01](https://github.com/TheAlgorithms/Java/blob/master/ProjectEuler/Problem01.java)
-  * [Problem02](https://github.com/TheAlgorithms/Java/blob/master/ProjectEuler/Problem02.java)
-  * [Problem03](https://github.com/TheAlgorithms/Java/blob/master/ProjectEuler/Problem03.java)
-  * [Problem04](https://github.com/TheAlgorithms/Java/blob/master/ProjectEuler/Problem04.java)
-  * [Problem06](https://github.com/TheAlgorithms/Java/blob/master/ProjectEuler/Problem06.java)
-  * [Problem07](https://github.com/TheAlgorithms/Java/blob/master/ProjectEuler/Problem07.java)
-  * [Problem09](https://github.com/TheAlgorithms/Java/blob/master/ProjectEuler/Problem09.java)
-  * [Problem10](https://github.com/TheAlgorithms/Java/blob/master/ProjectEuler/Problem10.java)
-  * [Problem12](https://github.com/TheAlgorithms/Java/blob/master/ProjectEuler/Problem12.java)
-
 ## Searches
   * [BinarySearch](https://github.com/TheAlgorithms/Java/blob/master/Searches/BinarySearch.java)
-  * [IBSearch test](https://github.com/TheAlgorithms/Java/blob/master/Searches/IBSearch_test.java)
   * [InterpolationSearch](https://github.com/TheAlgorithms/Java/blob/master/Searches/InterpolationSearch.java)
   * [IterativeBinarySearch](https://github.com/TheAlgorithms/Java/blob/master/Searches/IterativeBinarySearch.java)
   * [IterativeTernarySearch](https://github.com/TheAlgorithms/Java/blob/master/Searches/IterativeTernarySearch.java)
@@ -274,15 +262,15 @@
   * [SortUtils](https://github.com/TheAlgorithms/Java/blob/master/Sorts/SortUtils.java)
   * [TimSort](https://github.com/TheAlgorithms/Java/blob/master/Sorts/TimSort.java)
 
-## strings
+## Strings
-  * [Alphabetical](https://github.com/TheAlgorithms/Java/blob/master/strings/Alphabetical.java)
+  * [Alphabetical](https://github.com/TheAlgorithms/Java/blob/master/Strings/Alphabetical.java)
-  * [CharactersSame](https://github.com/TheAlgorithms/Java/blob/master/strings/CharactersSame.java)
+  * [CharactersSame](https://github.com/TheAlgorithms/Java/blob/master/Strings/CharactersSame.java)
-  * [CheckAnagrams](https://github.com/TheAlgorithms/Java/blob/master/strings/CheckAnagrams.java)
+  * [CheckAnagrams](https://github.com/TheAlgorithms/Java/blob/master/Strings/CheckAnagrams.java)
-  * [CheckVowels](https://github.com/TheAlgorithms/Java/blob/master/strings/CheckVowels.java)
+  * [CheckVowels](https://github.com/TheAlgorithms/Java/blob/master/Strings/CheckVowels.java)
-  * [HorspoolSearch](https://github.com/TheAlgorithms/Java/blob/master/strings/HorspoolSearch.java)
+  * [HorspoolSearch](https://github.com/TheAlgorithms/Java/blob/master/Strings/HorspoolSearch.java)
-  * [Lower](https://github.com/TheAlgorithms/Java/blob/master/strings/Lower.java)
+  * [Lower](https://github.com/TheAlgorithms/Java/blob/master/Strings/Lower.java)
-  * [Palindrome](https://github.com/TheAlgorithms/Java/blob/master/strings/Palindrome.java)
+  * [Palindrome](https://github.com/TheAlgorithms/Java/blob/master/Strings/Palindrome.java)
-  * [Pangram](https://github.com/TheAlgorithms/Java/blob/master/strings/Pangram.java)
+  * [Pangram](https://github.com/TheAlgorithms/Java/blob/master/Strings/Pangram.java)
-  * [ReverseString](https://github.com/TheAlgorithms/Java/blob/master/strings/ReverseString.java)
+  * [ReverseString](https://github.com/TheAlgorithms/Java/blob/master/Strings/ReverseString.java)
-  * [Rotation](https://github.com/TheAlgorithms/Java/blob/master/strings/Rotation.java)
+  * [Rotation](https://github.com/TheAlgorithms/Java/blob/master/Strings/Rotation.java)
-  * [Upper](https://github.com/TheAlgorithms/Java/blob/master/strings/Upper.java)
+  * [Upper](https://github.com/TheAlgorithms/Java/blob/master/Strings/Upper.java)

DataStructures/Graphs/A_Star.java

@@ -2,32 +2,33 @@
 	Time Complexity = O(E), where E is equal to the number of edges
 */
 
-package A_Star;
+package Graphs;
 
+import java.lang.reflect.Array;
 import java.util.*;
 
 public class A_Star {
 
   private static class Graph {
     // Graph's structure can be changed only applying changes to this class.
-    private ArrayList<Edge>[] graph;
+    private ArrayList<ArrayList<Edge>> graph;
 
     // Initialise ArrayLists in Constructor
     public Graph(int size) {
-      this.graph = new ArrayList[size];
+      this.graph = new ArrayList<>();
       for (int i = 0; i < size; i++) {
-        this.graph[i] = new ArrayList<>();
+        this.graph.set(i, new ArrayList<>());
       }
     }
 
     private ArrayList<Edge> getNeighbours(int from) {
-      return this.graph[from];
+      return this.graph.get(from);
     }
 
     // Graph is bidirectional, for just one direction remove second instruction of this method.
     private void addEdge(Edge edge) {
-      this.graph[edge.getFrom()].add(new Edge(edge.getFrom(), edge.getTo(), edge.getWeight()));
+      this.graph.get(edge.getFrom()).add(new Edge(edge.getFrom(), edge.getTo(), edge.getWeight()));
-      this.graph[edge.getTo()].add(new Edge(edge.getTo(), edge.getFrom(), edge.getWeight()));
+      this.graph.get(edge.getTo()).add(new Edge(edge.getTo(), edge.getFrom(), edge.getWeight()));
     }
   }
 
@@ -83,7 +84,7 @@ public class A_Star {
     private void printSolution() {
       if (this.path != null)
         System.out.println(
-            "Optimal path: " + this.path.toString() + ", distance: " + this.distance);
+            "Optimal path: " + this.path + ", distance: " + this.distance);
       else System.out.println("There is no path available to connect the points");
     }
   }
@@ -129,13 +130,13 @@ public class A_Star {
 
     Graph graph = new Graph(20);
     ArrayList<Integer> graphData =
-        new ArrayList<>(
+            new ArrayList<>(
-            Arrays.asList(
+                    Arrays.asList(
-                0, 19, 75, null, 0, 15, 140, null, 0, 16, 118, null, 19, 12, 71, null, 12, 15, 151,
+                            0, 19, 75, null, 0, 15, 140, null, 0, 16, 118, null, 19, 12, 71, null, 12, 15, 151,
-                null, 16, 9, 111, null, 9, 10, 70, null, 10, 3, 75, null, 3, 2, 120, null, 2, 14,
+                            null, 16, 9, 111, null, 9, 10, 70, null, 10, 3, 75, null, 3, 2, 120, null, 2, 14,
-                146, null, 2, 13, 138, null, 2, 6, 115, null, 15, 14, 80, null, 15, 5, 99, null, 14,
+                            146, null, 2, 13, 138, null, 2, 6, 115, null, 15, 14, 80, null, 15, 5, 99, null, 14,
-                13, 97, null, 5, 1, 211, null, 13, 1, 101, null, 6, 1, 160, null, 1, 17, 85, null,
+                            13, 97, null, 5, 1, 211, null, 13, 1, 101, null, 6, 1, 160, null, 1, 17, 85, null,
-                17, 7, 98, null, 7, 4, 86, null, 17, 18, 142, null, 18, 8, 92, null, 8, 11, 87));
+                            17, 7, 98, null, 7, 4, 86, null, 17, 18, 142, null, 18, 8, 92, null, 8, 11, 87));
     initializeGraph(graph, graphData);
 
     PathAndDistance solution = aStar(3, 1, graph, heuristic);
@@ -147,10 +148,10 @@ public class A_Star {
     // estimated value
     // given by the heuristic function to reach the destination point from the current point.
     PriorityQueue<PathAndDistance> queue =
-        new PriorityQueue<>(Comparator.comparingInt(a -> (a.getDistance() + a.getEstimated())));
+            new PriorityQueue<>(Comparator.comparingInt(a -> (a.getDistance() + a.getEstimated())));
 
     // dummy data to start the algorithm from the beginning point
-    queue.add(new PathAndDistance(0, new ArrayList<>(Arrays.asList(from)), 0));
+    queue.add(new PathAndDistance(0, new ArrayList<>(List.of(from)), 0));
 
     boolean solutionFound = false;
     PathAndDistance currentData = new PathAndDistance(-1, null, -1);

DataStructures/HashMap/Hashing/HashMapLinearProbing.java

@@ -20,7 +20,7 @@ public class HashMapLinearProbing {
   public HashMapLinearProbing(int hsize) {
     this.buckets = new Integer[hsize];
     this.hsize = hsize;
-    this.AVAILABLE = new Integer(Integer.MIN_VALUE);
+    this.AVAILABLE = Integer.MIN_VALUE;
     this.size = 0;
   }
 
@@ -44,7 +44,7 @@ public class HashMapLinearProbing {
    * @param key the desired key to be inserted in the hash map
    */
   public void insertHash(int key) {
-    Integer wrappedInt = new Integer(key);
+    Integer wrappedInt = key;
     int hash = hashing(key);
 
     if (isFull()) {
@@ -73,7 +73,7 @@ public class HashMapLinearProbing {
    * @param key the desired key to be deleted
    */
   public void deleteHash(int key) {
-    Integer wrappedInt = new Integer(key);
+    Integer wrappedInt = key;
     int hash = hashing(key);
 
     if (isEmpty()) {
@@ -115,7 +115,7 @@ public class HashMapLinearProbing {
    * @return int the index where the key is located
    */
   public int findHash(int key) {
-    Integer wrappedInt = new Integer(key);
+    Integer wrappedInt = key;
     int hash = hashing(key);
 
     if (isEmpty()) {

DataStructures/Stacks/README.md

@@ -2,7 +2,7 @@
 
 stack is an ADT (abstract data type ) that act like list of objects but there is a diffrents.
 
-stack act is *LIFO* (Last In First Out), it means that when we want to get an element from the stack we get the last element in the stack.
+stack act is _LIFO_ (Last In First Out), it means that when we want to get an element from the stack we get the last element in the stack.
 
 stack is bast on two methods ( functions)
 
@@ -14,7 +14,6 @@ for example: we have `1, 3, 5` in stack, then we call push(9),
 
 `9` will add to last index of stack -> `1, 3, 5 , 9`
 
-
 **pop**: remove the last element from stack.
 for example: we have `1, 3, 5 , 9` in stack, then we call pop(),
 

DataStructures/Trees/AVLSimple

@@ -82,7 +82,7 @@ public class AVLTree {
 		System.out.println(this.root.height);
 	}
 	private void display (Node node) {
-		String str="";
+		Strings str="";
 		if(node.left!=null)
 			str+=node.left.data+"=>";
 		else

DivideAndConquer/ClosestPair.java

@@ -1,16 +1,15 @@
-package divideconquer;
+package DivideAndConquer;
+
+import java.io.IOException;
 
 /**
  * For a set of points in a coordinates system (10000 maximum), ClosestPair class calculates the two
  * closest points.
- *
- * @author: anonymous
- * @author: Marisa Afuera
  */
 public final class ClosestPair {
 
   /** Number of points */
-  int numberPoints = 0;
+  int numberPoints;
   /** Input data, maximum 10000. */
   private Location[] array;
   /** Minimum point coordinate. */
@@ -40,8 +39,8 @@ public final class ClosestPair {
   /** Location class is an auxiliary type to keep points coordinates. */
   public static class Location {
 
-    double x = 0;
+    double x;
-    double y = 0;
+    double y;
 
     /**
      * @param xpar (IN Parameter) x coordinate <br>
@@ -172,9 +171,9 @@ public final class ClosestPair {
     // divide-right array
     System.arraycopy(divideArray, divideX, rightArray, 0, indexNum - divideX);
 
-    double minLeftArea = 0; // Minimum length of left array
+    double minLeftArea; // Minimum length of left array
-    double minRightArea = 0; // Minimum length of right array
+    double minRightArea; // Minimum length of right array
-    double minValue = 0; // Minimum lengt
+    double minValue; // Minimum lengt
 
     minLeftArea = closestPair(leftArray, divideX); // recursive closestPair
     minRightArea = closestPair(rightArray, indexNum - divideX);
@@ -209,7 +208,7 @@ public final class ClosestPair {
     }
     yQuickSort(firstWindow, 0, secondCount - 1); // Sort by y coordinates
     /* Coordinates in Window */
-    double length = 0;
+    double length;
     // size comparison within window
     for (int i = 0; i < secondCount - 1; i++) {
       for (int j = (i + 1); j < secondCount; j++) {
@@ -246,9 +245,9 @@ public final class ClosestPair {
   public double bruteForce(final Location[] arrayParam) {
 
     double minValue = Double.MAX_VALUE; // minimum distance
-    double length = 0;
+    double length;
-    double xGap = 0; // Difference between x coordinates
+    double xGap; // Difference between x coordinates
-    double yGap = 0; // Difference between y coordinates
+    double yGap; // Difference between y coordinates
     double result = 0;
 
     if (arrayParam.length == 2) {
@@ -297,7 +296,6 @@ public final class ClosestPair {
    * main function: execute class.
    *
    * @param args (IN Parameter) <br>
-   * @throws IOException If an input or output exception occurred
    */
   public static void main(final String[] args) {
 

DivideAndConquer/SkylineAlgorithm.java

@@ -1,4 +1,4 @@
-package divideconquer;
+package DivideAndConquer;
 
 import java.util.ArrayList;
 import java.util.Comparator;

ProjectEuler/Problem01.java

@@ -1,51 +0,0 @@
-package ProjectEuler;
-
-/**
- * If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9.
- * The sum of these multiples is 23.
- *
- * <p>Find the sum of all the multiples of 3 or 5 below 1000.
- *
- * <p>Link: https://projecteuler.net/problem=1
- */
-public class Problem01 {
-  public static void main(String[] args) {
-    int[][] testNumber = {
-      {3, 0},
-      {4, 3},
-      {10, 23},
-      {1000, 233168},
-      {-1, 0}
-    };
-
-    for (int[] ints : testNumber) {
-      assert solution1(ints[0]) == ints[1];
-      assert solution2(ints[0]) == ints[1];
-    }
-  }
-
-  private static int solution1(int n) {
-    int sum = 0;
-    for (int i = 3; i < n; ++i) {
-      if (i % 3 == 0 || i % 5 == 0) {
-        sum += i;
-      }
-    }
-    return sum;
-  }
-
-  private static int solution2(int n) {
-    int sum = 0;
-
-    int terms = (n - 1) / 3;
-    sum += terms * (6 + (terms - 1) * 3) / 2;
-
-    terms = (n - 1) / 5;
-    sum += terms * (10 + (terms - 1) * 5) / 2;
-
-    terms = (n - 1) / 15;
-    sum -= terms * (30 + (terms - 1) * 15) / 2;
-
-    return sum;
-  }
-}

ProjectEuler/Problem02.java

@@ -1,43 +0,0 @@
-package ProjectEuler;
-
-/**
- * Each new term in the Fibonacci sequence is generated by adding the previous two terms. By
- * starting with 1 and 2, the first 10 terms will be:
- *
- * <p>1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
- *
- * <p>By considering the terms in the Fibonacci sequence whose values do not exceed four million,
- * find the sum of the even-valued terms.
- *
- * <p>Link: https://projecteuler.net/problem=2
- */
-public class Problem02 {
-  public static void main(String[] args) {
-    int[][] testNumbers = {
-      {10, 10}, /* 2 + 8 == 10 */
-      {15, 10}, /* 2 + 8 == 10 */
-      {2, 2},
-      {1, 0},
-      {89, 44} /* 2 + 8 + 34 == 44 */
-    };
-
-    for (int[] ints : testNumbers) {
-      assert solution1(ints[0]) == ints[1];
-    }
-  }
-
-  private static int solution1(int n) {
-    int sum = 0;
-    int first = 1;
-    int second = 2;
-    while (second <= n) {
-      if (second % 2 == 0) {
-        sum += second;
-      }
-      int temp = first + second;
-      first = second;
-      second = temp;
-    }
-    return sum;
-  }
-}

ProjectEuler/Problem03.java

@@ -1,62 +0,0 @@
-package ProjectEuler;
-
-/**
- * The prime factors of 13195 are 5, 7, 13 and 29.
- *
- * <p>What is the largest prime factor of the number 600851475143 ?
- *
- * <p>Link: https://projecteuler.net/problem=3
- */
-public class Problem03 {
-
-  /**
-   * Checks if a number is prime or not
-   *
-   * @param n the number
-   * @return {@code true} if {@code n} is prime
-   */
-  public static boolean isPrime(int n) {
-    if (n == 2) {
-      return true;
-    }
-    if (n < 2 || n % 2 == 0) {
-      return false;
-    }
-    for (int i = 3, limit = (int) Math.sqrt(n); i <= limit; i += 2) {
-      if (n % i == 0) {
-        return false;
-      }
-    }
-    return true;
-  }
-
-  /**
-   * Calculate all the prime factors of a number and return the largest
-   *
-   * @param n integer number
-   * @return the maximum prime factor of the given number
-   */
-  static long maxPrimeFactor(long n) {
-    for (int i = 2; i < n / 2; i++) {
-      if (isPrime(i))
-        while (n % i == 0) {
-          n /= i;
-        }
-    }
-    return n;
-  }
-
-  public static void main(String[] args) {
-    int[][] testNumbers = {
-      {87, 29},
-      {10, 5},
-      {21, 7},
-      {657, 73},
-      {777, 37}
-    };
-    for (int[] num : testNumbers) {
-      assert Problem03.maxPrimeFactor(num[0]) == num[1];
-    }
-    assert Problem03.maxPrimeFactor(600851475143L) == 6857;
-  }
-}

ProjectEuler/Problem04.java

@@ -1,41 +0,0 @@
-package ProjectEuler;
-
-/**
- * A palindromic number reads the same both ways. The largest palindrome made from the product of
- * two 2-digit numbers is 9009 = 91 × 99.
- *
- * <p>Find the largest palindrome made from the product of two 3-digit numbers.
- *
- * <p>link: https://projecteuler.net/problem=4
- */
-public class Problem04 {
-  public static void main(String[] args) {
-
-    assert solution1(10000) == -1;
-    assert solution1(20000) == 19591; /* 19591 == 143*137 */
-    assert solution1(30000) == 29992; /* 29992 == 184*163 */
-    assert solution1(40000) == 39893; /* 39893 == 287*139 */
-    assert solution1(50000) == 49894; /* 49894 == 494*101 */
-    assert solution1(60000) == 59995; /* 59995 == 355*169 */
-    assert solution1(70000) == 69996; /* 69996 == 614*114 */
-    assert solution1(80000) == 79897; /* 79897 == 733*109 */
-    assert solution1(90000) == 89798; /* 89798 == 761*118 */
-    assert solution1(100000) == 99999; /* 100000 == 813*123 */
-  }
-
-  private static int solution1(int n) {
-    for (int i = n - 1; i >= 10000; --i) {
-      String strNumber = String.valueOf(i);
-
-      /* Test if strNumber is palindrome */
-      if (new StringBuilder(strNumber).reverse().toString().equals(strNumber)) {
-        for (int divisor = 999; divisor >= 100; --divisor) {
-          if (i % divisor == 0 && String.valueOf(i / divisor).length() == 3) {
-            return i;
-          }
-        }
-      }
-    }
-    return -1; /* not found */
-  }
-}

ProjectEuler/Problem06.java

@@ -1,42 +0,0 @@
-package ProjectEuler;
-
-/**
- * The sum of the squares of the first ten natural numbers is, 1^2 + 2^2 + ... + 10^2 = 385 The
- * square of the sum of the first ten natural numbers is, (1 + 2 + ... + 10)^2 = 552 = 3025 Hence
- * the difference between the sum of the squares of the first ten natural numbers and the square of
- * the sum is 3025 − 385 = 2640. Find the difference between the sum of the squares of the first N
- * natural numbers and the square of the sum.
- *
- * <p>link: https://projecteuler.net/problem=6
- */
-public class Problem06 {
-  public static void main(String[] args) {
-    int[][] testNumbers = {
-      {10, 2640},
-      {15, 13160},
-      {20, 41230},
-      {50, 1582700}
-    };
-
-    for (int[] testNumber : testNumbers) {
-      assert solution1(testNumber[0]) == testNumber[1]
-          && solutions2(testNumber[0]) == testNumber[1];
-    }
-  }
-
-  private static int solution1(int n) {
-    int sum1 = 0;
-    int sum2 = 0;
-    for (int i = 1; i <= n; ++i) {
-      sum1 += i * i;
-      sum2 += i;
-    }
-    return sum2 * sum2 - sum1;
-  }
-
-  private static int solutions2(int n) {
-    int sumOfSquares = n * (n + 1) * (2 * n + 1) / 6;
-    int squareOfSum = (int) Math.pow((n * (n + 1) / 2.0), 2);
-    return squareOfSum - sumOfSquares;
-  }
-}

ProjectEuler/Problem07.java

@@ -1,60 +0,0 @@
-package ProjectEuler;
-
-/**
- * By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is
- * 13.
- *
- * <p>What is the 10 001st prime number?
- *
- * <p>link: https://projecteuler.net/problem=7
- */
-public class Problem07 {
-  public static void main(String[] args) {
-    int[][] testNumbers = {
-      {1, 2},
-      {2, 3},
-      {3, 5},
-      {4, 7},
-      {5, 11},
-      {6, 13},
-      {20, 71},
-      {50, 229},
-      {100, 541}
-    };
-    for (int[] number : testNumbers) {
-      assert solution1(number[0]) == number[1];
-    }
-  }
-
-  /***
-   * Checks if a number is prime or not
-   * @param number the number
-   * @return {@code true} if {@code number} is prime
-   */
-  private static boolean isPrime(int number) {
-    if (number == 2) {
-      return true;
-    }
-    if (number < 2 || number % 2 == 0) {
-      return false;
-    }
-    for (int i = 3, limit = (int) Math.sqrt(number); i <= limit; i += 2) {
-      if (number % i == 0) {
-        return false;
-      }
-    }
-    return true;
-  }
-
-  private static int solution1(int n) {
-    int count = 0;
-    int number = 1;
-
-    while (count != n) {
-      if (isPrime(++number)) {
-        count++;
-      }
-    }
-    return number;
-  }
-}

ProjectEuler/Problem09.java

@@ -1,28 +0,0 @@
-package ProjectEuler;
-
-/**
- * A Pythagorean triplet is a set of three natural numbers, a < b < c, for which,
- *
- * <p>a^2 + b^2 = c^2 For example, 3^2 + 4^2 = 9 + 16 = 25 = 5^2.
- *
- * <p>There exists exactly one Pythagorean triplet for which a + b + c = 1000. Find the product abc.
- *
- * <p>link: https://projecteuler.net/problem=9
- */
-public class Problem09 {
-  public static void main(String[] args) {
-    assert solution1() == 31875000;
-  }
-
-  private static int solution1() {
-    for (int i = 0; i <= 300; ++i) {
-      for (int j = 0; j <= 400; ++j) {
-        int k = 1000 - i - j;
-        if (i * i + j * j == k * k) {
-          return i * j * k;
-        }
-      }
-    }
-    return -1; /* should not happen */
-  }
-}

ProjectEuler/Problem10.java

@@ -1,55 +0,0 @@
-package ProjectEuler;
-
-/**
- * The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.
- *
- * <p>Find the sum of all the primes below two million.
- *
- * <p>link: https://projecteuler.net/problem=10
- */
-public class Problem10 {
-  public static void main(String[] args) {
-    long[][] testNumbers = {
-      {2000000, 142913828922L},
-      {10000, 5736396},
-      {5000, 1548136},
-      {1000, 76127},
-      {10, 17},
-      {7, 10}
-    };
-
-    for (long[] testNumber : testNumbers) {
-      assert solution1(testNumber[0]) == testNumber[1];
-    }
-  }
-
-  /***
-   * Checks if a number is prime or not
-   * @param n the number
-   * @return {@code true} if {@code n} is prime
-   */
-  private static boolean isPrime(int n) {
-    if (n == 2) {
-      return true;
-    }
-    if (n < 2 || n % 2 == 0) {
-      return false;
-    }
-    for (int i = 3, limit = (int) Math.sqrt(n); i <= limit; i += 2) {
-      if (n % i == 0) {
-        return false;
-      }
-    }
-    return true;
-  }
-
-  private static long solution1(long n) {
-    long sum = 0;
-    for (int i = 2; i < n; ++i) {
-      if (isPrime(i)) {
-        sum += i;
-      }
-    }
-    return sum;
-  }
-}

ProjectEuler/Problem12.java

@@ -1,54 +0,0 @@
-package ProjectEuler;
-/**
- * The sequence of triangle numbers is generated by adding the natural numbers. So the 7th triangle
- * number would be 1 + 2 + 3 + 4 + 5 + 6 + 7 = 28. The first ten terms would be:
- *
- * <p>1, 3, 6, 10, 15, 21, 28, 36, 45, 55, ...
- *
- * <p>Let us list the factors of the first seven triangle numbers:
- *
- * <p>1: 1 3: 1,3 6: 1,2,3,6 10: 1,2,5,10 15: 1,3,5,15 21: 1,3,7,21 28: 1,2,4,7,14,28 We can see
- * that 28 is the first triangle number to have over five divisors.
- *
- * <p>What is the value of the first triangle number to have over five hundred divisors?
- *
- * <p>link: https://projecteuler.net/problem=12
- */
-public class Problem12 {
-
-  /** Driver Code */
-  public static void main(String[] args) {
-    assert solution1(500) == 76576500;
-  }
-
-  /* returns the nth triangle number; that is, the sum of all the natural numbers less than, or equal to, n */
-  public static int triangleNumber(int n) {
-    int sum = 0;
-    for (int i = 0; i <= n; i++) sum += i;
-    return sum;
-  }
-
-  public static int solution1(int number) {
-    int j = 0; // j represents the jth triangle number
-    int n = 0; // n represents the triangle number corresponding to j
-    int numberOfDivisors = 0; // number of divisors for triangle number n
-
-    while (numberOfDivisors <= number) {
-
-      // resets numberOfDivisors because it's now checking a new triangle number
-      // and also sets n to be the next triangle number
-      numberOfDivisors = 0;
-      j++;
-      n = triangleNumber(j);
-
-      // for every number from 1 to the square root of this triangle number,
-      // count the number of divisors
-      for (int i = 1; i <= Math.sqrt(n); i++) if (n % i == 0) numberOfDivisors++;
-
-      // 1 to the square root of the number holds exactly half of the divisors
-      // so multiply it by 2 to include the other corresponding half
-      numberOfDivisors *= 2;
-    }
-    return n;
-  }
-}

README-ko.md

@@ -156,28 +156,28 @@ From [Wikipedia][binary-wiki]: 이진 탐색, (also known as half-interval searc
 
 ## 나머지 알고리즘에 대한 링크
 
-| 전환                                                            | 다이나믹프로그래밍(DP)                                                                    | 암호                                                                      | 그 외 것들                                              |
+| 전환                                                            | 다이나믹프로그래밍(DP)                                                                 | 암호                                                                      | 그 외 것들                                             |
-| --------------------------------------------------------------- | ----------------------------------------------------------------------------------------- | ------------------------------------------------------------------------- | ------------------------------------------------------- |
+| --------------------------------------------------------------- | -------------------------------------------------------------------------------------- | ------------------------------------------------------------------------- | ------------------------------------------------------ |
-| [Any Base to Any Base](Conversions/AnyBaseToAnyBase.java)       | [Coin Change](Dynamic%20Programming/CoinChange.java)                                      | [Caesar](ciphers/Caesar.java)                                             | [Heap Sort](misc/heap_sort.java)                        |
+| [Any Base to Any Base](Conversions/AnyBaseToAnyBase.java)       | [Coin Change](DynamicProgramming/CoinChange.java)                                      | [Caesar](Ciphers/Caesar.java)                                             | [Heap Sort](Sorts/HeapSort.java)                       |
-| [Any Base to Decimal](Conversions/AnyBaseToDecimal.java)        | [Egg Dropping](Dynamic%20Programming/EggDropping.java)                                    | [Columnar Transposition Cipher](ciphers/ColumnarTranspositionCipher.java) | [Palindromic Prime Checker](misc/PalindromicPrime.java) |
+| [Any Base to Decimal](Conversions/AnyBaseToDecimal.java)        | [Egg Dropping](DynamicProgramming/EggDropping.java)                                    | [Columnar Transposition Cipher](Ciphers/ColumnarTranspositionCipher.java) | [Palindromic Prime Checker](Misc/PalindromePrime.java) |
-| [Binary to Decimal](Conversions/BinaryToDecimal.java)           | [Fibonacci](Dynamic%20Programming/Fibonacci.java)                                         | [RSA](ciphers/RSA.java)                                                   | More soon...                                            |
+| [Binary to Decimal](Conversions/BinaryToDecimal.java)           | [Fibonacci](DynamicProgramming/Fibonacci.java)                                         | [RSA](Ciphers/RSA.java)                                                   | More soon...                                           |
-| [Binary to HexaDecimal](Conversions/BinaryToHexadecimal.java)   | [Kadane Algorithm](Dynamic%20Programming/KadaneAlgorithm.java)                            | more coming soon...                                                       |
+| [Binary to HexaDecimal](Conversions/BinaryToHexadecimal.java)   | [Kadane Algorithm](DynamicProgramming/KadaneAlgorithm.java)                            | more coming soon...                                                       |
-| [Binary to Octal](Conversions/BinaryToOctal.java)               | [Knapsack](Dynamic%20Programming/Knapsack.java)                                           |
+| [Binary to Octal](Conversions/BinaryToOctal.java)               | [Knapsack](DynamicProgramming/Knapsack.java)                                           |
-| [Decimal To Any Base](Conversions/DecimalToAnyBase.java)        | [Longest Common Subsequence](Dynamic%20Programming/LongestCommonSubsequence.java)         |
+| [Decimal To Any Base](Conversions/DecimalToAnyBase.java)        | [Longest Common Subsequence](DynamicProgramming/LongestCommonSubsequence.java)         |
-| [Decimal To Binary](Conversions/DecimalToBinary.java)           | [Longest Increasing Subsequence](Dynamic%20Programming/LongestIncreasingSubsequence.java) |
+| [Decimal To Binary](Conversions/DecimalToBinary.java)           | [Longest Increasing Subsequence](DynamicProgramming/LongestIncreasingSubsequence.java) |
-| [Decimal To Hexadecimal](Conversions/DecimalToHexaDecimal.java) | [Rod Cutting](Dynamic%20Programming/RodCutting.java)                                      |
+| [Decimal To Hexadecimal](Conversions/DecimalToHexaDecimal.java) | [Rod Cutting](DynamicProgramming/RodCutting.java)                                      |
-| and much more...                                                | and more...                                                                               |
+| and much more...                                                | and more...                                                                            |
 
 ### 자료 구조
 
-| 그래프                                                            | 힙                                                             | 리스트                                                        | 큐                                                                          |
+| 그래프                                                  | 힙                                                             | 리스트                                                        | 큐                                                                          |
-| ----------------------------------------------------------------- | -------------------------------------------------------------- | ------------------------------------------------------------- | --------------------------------------------------------------------------- |
+| ------------------------------------------------------- | -------------------------------------------------------------- | ------------------------------------------------------------- | --------------------------------------------------------------------------- |
-| [너비우선탐색](DataStructures/Graphs/BFS.java)                    | [빈 힙 예외처리](DataStructures/Heaps/EmptyHeapException.java) | [원형 연결리스트](DataStructures/Lists/CircleLinkedList.java) | [제너릭 어레이 리스트 큐](DataStructures/Queues/GenericArrayListQueue.java) |
+|                                                         | [빈 힙 예외처리](DataStructures/Heaps/EmptyHeapException.java) | [원형 연결리스트](DataStructures/Lists/CircleLinkedList.java) | [제너릭 어레이 리스트 큐](DataStructures/Queues/GenericArrayListQueue.java) |
-| [깊이우선탐색](DataStructures/Graphs/DFS.java)                    | [힙](DataStructures/Heaps/Heap.java)                           | [이중 연결리스트](DataStructures/Lists/DoublyLinkedList.java) | [큐](DataStructures/Queues/Queues.java)                                     |
+|                                                         | [힙](DataStructures/Heaps/Heap.java)                           | [이중 연결리스트](DataStructures/Lists/DoublyLinkedList.java) | [큐](DataStructures/Queues/Queues.java)                                     |
-| [그래프](DataStructures/Graphs/Graphs.java)                       | [힙 요소](DataStructures/Heaps/HeapElement.java)               | [단순 연결리스트](DataStructures/Lists/SinglyLinkedList.java) |
+| [그래프](DataStructures/Graphs/Graphs.java)             | [힙 요소](DataStructures/Heaps/HeapElement.java)               | [단순 연결리스트](DataStructures/Lists/SinglyLinkedList.java) |
-| [크루스칼 알고리즘](DataStructures/Graphs/KruskalsAlgorithm.java) | [최대힙](Data%Structures/Heaps/MaxHeap.java)                   |
+| [크루스칼 알고리즘](DataStructures/Graphs/Kruskal.java) | [최대힙](DataStructures/Heaps/MaxHeap.java)                    |
-| [행렬 그래프](DataStructures/Graphs/MatrixGraphs.java)            | [최소힙](DataStructures/Heaps/MinHeap.java)                    |
+| [행렬 그래프](DataStructures/Graphs/MatrixGraphs.java)  | [최소힙](DataStructures/Heaps/MinHeap.java)                    |
-| [프림 최소신장트리](DataStructures/Graphs/PrimMST.java)           |
+| [프림 최소신장트리](DataStructures/Graphs/PrimMST.java) |
 
 | 스택                                                            | 트리                                              |
 | --------------------------------------------------------------- | ------------------------------------------------- |
@@ -187,5 +187,5 @@ From [Wikipedia][binary-wiki]: 이진 탐색, (also known as half-interval searc
 
 - [Bags](DataStructures/Bags/Bag.java)
 - [Buffer](DataStructures/Buffers/CircularBuffer.java)
-- [HashMap](DataStructures/HashMap/HashMap.java)
+- [HashMap](DataStructures/HashMap/Hashing/HashMap.java)
-- [Matrix](DataStructures/Matrix/Matrix.java)
+-

README.md

@@ -1,10 +1,8 @@
-[![Gitpod ready-to-code](https://img.shields.io/badge/Gitpod-ready--to--code-blue?logo=gitpod)](https://gitpod.io/#https://github.com/TheAlgorithms/Java)
-
 # The Algorithms - Java
-[![Build Status](https://api.travis-ci.com/TheAlgorithms/Java.svg?branch=master)](https://travis-ci.com/TheAlgorithms/Java) 
+
-[![Donate](https://img.shields.io/badge/Donate-PayPal-green.svg)](https://www.paypal.me/TheAlgorithms/100)
+[![Build](https://github.com/TheAlgorithms/Java/actions/workflows/build.yml/badge.svg?branch=master)](https://github.com/TheAlgorithms/Java/actions/workflows/build.yml)
-[![Discord chat](https://img.shields.io/discord/808045925556682782.svg?logo=discord&colorB=7289DA&style=flat-square)](https://discord.gg/c7MnfGFGa6) 
+[![Discord chat](https://img.shields.io/discord/808045925556682782.svg?logo=discord&colorB=7289DA&style=flat-square)](https://discord.gg/c7MnfGFGa6)
-[![Gitter chat](https://img.shields.io/badge/Chat-Gitter-ff69b4.svg?label=Chat&logo=gitter&style=flat-square)](https://gitter.im/TheAlgorithms) 
+[![Gitpod ready-to-code](https://img.shields.io/badge/Gitpod-ready--to--code-blue?logo=gitpod)](https://gitpod.io/#https://github.com/TheAlgorithms/Java)
 
 
 You can run and edit the algorithms, or contribute to them using Gitpod.io (a free online development environment) with a single click.

REVIEWER.md

@@ -1,13 +0,0 @@
-# Guidelines for reviewers and maintainers
-
-Following are some guidelines for contributors who are providing reviews to the pull-requests.
-
-1. On any given pull-request, there only one reviewer should be active at a time. Once the reviewer is done, others may add short comments or any further reviews as needed. Again, one at a time.
-2. Assigning reviewers should be avoided unless the pull-request is for a particular task the reviewer is more proficient in.
-3. Any contributor who has had their code merged into the repo can provide with reviews as they have gone through the repo standards at least once before. The reviewer will be on a first-come-first serve basis.
-4. Most repositories have a check-list in the description for pull-requests. Many times, the contributors are not following them and simply remove the checklist or checkthem without taking the time to review the checklist items. These contributors are almost always copying the code from somewhere. These should be pointed out politely and reviews should be blocked until the contributor updates the basic code structure per the checklist and the repo standards.
-5. The reviewers should label every pull-request appropriately - including "invalid" as the case may be.
-6. Some pull-requests have existing duplicate code or duplicate pull-requests or sometimes, a novice might create a new pull-request for every new commit. This is a daunting task but one of the responsibility of a reviewer.
-7. Discourage creating branches on the repo but rather fork the repo to the respective userspace and contribute from that fork.
-8. Some repos - C & C++ - have collaboration with GitPod wherein the code and the contribution can be executed and tested online with relative simplicity. It also contains tools necessary to perform debug and CI checks without installing any tools. Encourage contributors to utilize the feature. Reviewers can test the contributed algorithms online without worrying about forks and branches.
-9. There should not be any hurry to merge pull-requests. Since the repos are educational, better to get the contributions right even if it takes a bit longer to review. Encourage patience and develop debugging skills of contributors.

Searches/IBSearch_test.java

@@ -1,32 +0,0 @@
-import static org.junit.jupiter.api.Assertions.*;
-
-import org.junit.jupiter.api.Test;
-
-public class IterativeBinarySearch_Test {
-
-  //	kiem thu luong du lieu
-  //	ham search dung de tim key trong mang da xap xep
-  //	dua theo tieu chi all-du path tim dc 4 tescase
-  Integer[] arr = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
-  IterativeBinarySearch search = new IterativeBinarySearch();
-
-  @Test
-  void tc1_key_khong_co_trong_mang() {
-    assertTrue(search.find(arr, 11) == -1);
-  }
-
-  @Test
-  void tc2_key_nam_chinh_giua_mang() {
-    assertTrue(search.find(arr, 5) == 5);
-  }
-
-  @Test
-  void tc3_key_nam_cuoi_mang() {
-    assertTrue(search.find(arr, 10) == 10);
-  }
-
-  @Test
-  void tc4_key_nam_dau_mang() {
-    assertTrue(search.find(arr, 0) == 0);
-  }
-}

Strings/Alphabetical.java

@@ -1,4 +1,4 @@
-package strings;
+package Strings;
 
 /**
  * Alphabetical order is a system whereby character strings are placed in order based on the

Strings/CharactersSame.java

@@ -1,4 +1,4 @@
-package strings;
+package Strings;
 
 public class CharactersSame {
 

Strings/CheckAnagrams.java

@@ -1,4 +1,4 @@
-package strings;
+package Strings;
 
 import java.util.HashMap;
 import java.util.Map;

Strings/CheckVowels.java

@@ -1,4 +1,4 @@
-package strings;
+package Strings;
 
 /**
  * Vowel Count is a system whereby character strings are placed in order based on the position of
@@ -33,7 +33,7 @@ class CheckVowels {
    * @param input a string prints the count of vowels
    */
   public static void countVowels(String input) {
-    input.toLowerCase();
+    input = input.toLowerCase();
     int count = 0;
     int i = 0;
     while (i < input.length()) {

Strings/HorspoolSearch.java

@@ -1,4 +1,4 @@
-package strings;
+package Strings;
 
 import java.util.HashMap;
 

Strings/Lower.java

@@ -1,4 +1,4 @@
-package strings;
+package Strings;
 
 public class Lower {
 

Strings/Palindrome.java

@@ -1,4 +1,4 @@
-package strings;
+package Strings;
 
 /** Wikipedia: https://en.wikipedia.org/wiki/Palindrome */
 class Palindrome {

Strings/Pangram.java

@@ -1,4 +1,4 @@
-package strings;
+package Strings;
 
 /** Wikipedia: https://en.wikipedia.org/wiki/Pangram */
 public class Pangram {

Strings/ReverseString.java

@@ -1,4 +1,4 @@
-package strings;
+package Strings;
 
 /** Reverse String using different version */
 public class ReverseString {

Strings/Rotation.java

@@ -1,4 +1,4 @@
-package strings;
+package Strings;
 
 /**
  * Given a string, moving several characters in front of the string to the end of the string. For

Strings/Upper.java

@@ -1,4 +1,4 @@
-package strings;
+package Strings;
 
 public class Upper {