Vigenere Cipher Implementation in Java..

I was inspired by "The Code Book". Explanation here!

VigenereCipherEncrypter.java

package biz.tugay.cipher.vigenere;
 
public class VigenereCipherEncrypter {
 
    public final String vigenereCipher(final char[] clearText, final char[] key) {
        final StringBuilder stringBuilder = new StringBuilder(clearText.length);
 
        for (int i = 0; i < clearText.length; i++) {
            final char cipherRow = key[i % key.length];
            char cipherChar = (char) (clearText[i] + (cipherRow - 'A'));
 
            if (cipherChar > 90) {
                cipherChar = (char) (cipherChar - ('Z' - 'A' + 1));
            }
 
            stringBuilder.append(cipherChar);
        }
 
        return stringBuilder.toString();
    }
}

Here is a simple test:

import biz.tugay.cipher.vigenere.VigenereCipherEncrypter;
 
public class Main {
 
    public static void main(String[] args) {
        String clearText = "ATTACKATDAWN";
        String key = "LEMON";
 
        final VigenereCipherEncrypter vigenereCipherEncrypter = new VigenereCipherEncrypter();
        final String cipherText = vigenereCipherEncrypter.vigenereCipher(clearText.toCharArray(), key.toCharArray());
 
        System.out.println(cipherText); // prints: LXFOPVEFRNHR
    }
}