Caesar Chipper

1. package com.sanfoundry.setandstring;

3. import java.util.Scanner;

5. public class CaesarCipher

6. {

7.     public static final String ALPHABET = "abcdefghijklmnopqrstuvwxyz";

9.     public static String encrypt(String plainText, int shiftKey)

10.     {

11.         plainText = plainText.toLowerCase();

12.         String cipherText = "";

13.         for (int i = 0; i < plainText.length(); i++)

14.         {

15.             int charPosition = ALPHABET.indexOf(plainText.charAt(i));

16.             int keyVal = (shiftKey + charPosition) % 26;

17.             char replaceVal = ALPHABET.charAt(keyVal);

18.             cipherText += replaceVal;

19.         }

20.         return cipherText;

21.     }

23.     public static String decrypt(String cipherText, int shiftKey)

24.     {

25.         cipherText = cipherText.toLowerCase();

26.         String plainText = "";

27.         for (int i = 0; i < cipherText.length(); i++)

28.         {

29.             int charPosition = ALPHABET.indexOf(cipherText.charAt(i));

30.             int keyVal = (charPosition - shiftKey) % 26;

31.             if (keyVal < 0)

32.             {

33.                 keyVal = ALPHABET.length() + keyVal;

34.             }

35.             char replaceVal = ALPHABET.charAt(keyVal);

36.             plainText += replaceVal;

37.         }

38.         return plainText;

39.     }

41.     public static void main(String[] args)

42.     {

43.         Scanner sc = new Scanner(System.in);

44.         System.out.println("Enter the String for Encryption: ");

45.         String message = new String();

46.         message = sc.next();

47.         System.out.println(encrypt(message, 3));

48.         System.out.println(decrypt(encrypt(message, 3), 3));

49.         sc.close();

50.     }

51. }