Experiment 1

Caesar Cipher

Perform Caesar Cipher on a given text using Java.

import java.util.Scanner;

class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.print("Enter a string to encrypt: ");
        String input = sc.nextLine();
        System.out.print("Enter shift value (0-25): ");
        int shift = sc.nextInt();
        char[] encryptedArray = input.toCharArray();
        encrypt(encryptedArray, shift);
        System.out.println("Encrypted String: " + new String(encryptedArray));

        sc.nextLine();

        System.out.print("Enter a string to decrypt: ");
        String input2 = sc.nextLine();
        char[] decryptedArray = input2.toCharArray();
        decrypt(decryptedArray, shift);
        System.out.println("Decrypted String: " + new String(decryptedArray));

        sc.close();
    }

    public static void encrypt(char[] str, int shift) {
        for (int i = 0; i < str.length; i++) {
            char ch = str[i];
            if (ch >= 'a' && ch <= 'z') {
                str[i] = (char) ((ch - 'a' + shift) % 26 + 'a');
            } else if (ch >= 'A' && ch <= 'Z') {
                str[i] = (char) ((ch - 'A' + shift) % 26 + 'A');
            }

        }
    }

    public static void decrypt(char[] str, int shift) {
        for (int i = 0; i < str.length; i++) {
            char ch = str[i];
            if (ch >= 'a' && ch <= 'z') {
                str[i] = (char) ((ch - 'a' - shift + 26) % 26 + 'a');
            } else if (ch >= 'A' && ch <= 'Z') {
                str[i] = (char) ((ch - 'A' - shift + 26) % 26 + 'A');
            }
        }
    }
}