Untitled

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Scanner;

public class CaesarCipher {
    static Scanner sc = new Scanner(System.in);
    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

    public static void main(String[] args) throws IOException {
        System.out.print("Enter any String: ");
        String str = br.readLine();

        System.out.print("\nEnter the Key: ");
        int key = sc.nextInt();

        // Normalize the key to handle large or negative values
        key = key % 26;

        String encrypted = encrypt(str, key);
        System.out.println("\nEncrypted String is: " + encrypted);

        String decrypted = decrypt(encrypted, key);
        System.out.println("\nDecrypted String is: " + decrypted);
    }

    public static String encrypt(String str, int key) {
        StringBuilder encrypted = new StringBuilder();

        for (int i = 0; i < str.length(); i++) {
            char currentChar = str.charAt(i);

            if (Character.isUpperCase(currentChar)) {
                currentChar = (char) ((currentChar + key - 'A') % 26 + 'A');
            } else if (Character.isLowerCase(currentChar)) {
                currentChar = (char) ((currentChar + key - 'a') % 26 + 'a');
            }

            encrypted.append(currentChar);
        }
        return encrypted.toString();
    }

    public static String decrypt(String str, int key) {
        StringBuilder decrypted = new StringBuilder();

        for (int i = 0; i < str.length(); i++) {
            char currentChar = str.charAt(i);

            if (Character.isUpperCase(currentChar)) {
                currentChar = (char) ((currentChar - key - 'A' + 26) % 26 + 'A');
            } else if (Character.isLowerCase(currentChar)) {
                currentChar = (char) ((currentChar - key - 'a' + 26) % 26 + 'a');
            }

            decrypted.append(currentChar);
        }
        return decrypted.toString();
    }
}