content: import java.util.Scanner;
  
  /**
   * The All Algorithms Project
   *
   * @contributor @chikaslocalhost
   */
  public class Ceasercipher {
  
      public static final String ALPHABET = "abcdefghijklmnopqrstuvwxyz";
  
      /**
       * Encryption using plaintext and shiftkey
       * 
       * @param plainText
       * @param shiftKey
       * @return
       */
      public static String encrypt(String plainText, int shiftKey) {
          plainText = plainText.toLowerCase();
          String cipherText = "";
          for (int i = 0; i < plainText.length(); i++) {
              int charPosition = ALPHABET.indexOf(plainText.charAt(i));
              int keyVal = (shiftKey + charPosition) % 26;
              char replaceVal = ALPHABET.charAt(keyVal);
              cipherText += replaceVal;
          }
          return cipherText;
      }
  
      /**
       * Decryption using encrypted value and shift key which used in encryption.
       * 
       * @param cipherText
       * @param shiftKey
       * @return
       */
      public static String decrypt(String cipherText, int shiftKey) {
          cipherText = cipherText.toLowerCase();
          String plainText = "";
          for (int i = 0; i < cipherText.length(); i++) {
              int charPosition = ALPHABET.indexOf(cipherText.charAt(i));
              int keyVal = (charPosition - shiftKey) % 26;
              if (keyVal < 0) {
                  keyVal = ALPHABET.length() + keyVal;
              }
              char replaceVal = ALPHABET.charAt(keyVal);
              plainText += replaceVal;
          }
          return plainText;
      }
  
      public static void main(String[] args) {
          Scanner sc = new Scanner(System.in);
          System.out.println("Enter the String for Encryption: ");
          String message = new String();
          message = sc.next();
          System.out.println(encrypt(message, 3));
          System.out.println(decrypt(encrypt(message, 3), 3));
          sc.close();
      }
  
  }
  