Question

5. Create a Java program to encrypt a word using the Cesar

cipher, one of the oldest ciphers known. To encrypt a word
you substitute each letter by the letter which is 3 spaces
down the alphabet. For example, a -> d, b ->e, ... So the
word CESAR would be encrypted as FHVDU.

Answer 1

Code:

import java.util.Scanner;

public class CaesarCipher {

public static void main(String[] args) {

Scanner scanner = new Scanner(System.in);

System.out.print("Enter a word to encrypt: ");

String word = scanner.nextLine();

System.out.print("Enter a shift amount: ");

int shift = scanner.nextInt();

String encrypted = encrypt(word, shift);

System.out.println("Encrypted word: " + encrypted);

}

public static String encrypt(String word, int shift) {

StringBuilder sb = new StringBuilder();

for (int i = 0; i < word.length(); i++) {

char c = word.charAt(i);

// Check if the character is a letter

if (Character.isLetter(c)) {

// Determine whether the letter is uppercase or lowercase

if (Character.isUpperCase(c)) {

// Apply the shift to the uppercase letter

c = (char) (((c - 'A' + shift) % 26) + 'A');

} else {

// Apply the shift to the lowercase letter

c = (char) (((c - 'a' + shift) % 26) + 'a');

}

}

// Add the character (either encrypted or unchanged) to the StringBuilder

sb.append(c);

}

// Return the encrypted word as a string

return sb.toString();

}

}