Correctly encode the uppercase letters

Question

package edu.secretcode;

import java.util.Scanner;

/**
 * Creates the secret code class.
 * 
 * @author
 * 
 */
public class SecretCode {
    /**
     * Perform the ROT13 operation
     * 
     * @param plainText
     *            the text to encode
     * @return the rot13'd encoding of plainText
     */

    public static String rotate13(String plainText) {
        StringBuffer cryptText = new StringBuffer("");
        for (int i = 0; i < plainText.length() - 1; i++) {
            char currentChar = plainText.charAt(i);
            currentChar = (char) ((char) (currentChar - 'A' + 13) % 26 + 'A');
            cryptText.append(currentChar);
            if (currentChar <= 'A' || currentChar >= 'Z') {
                cryptText.append(plainText.charAt(i));
            }

            else {
                currentChar = (char) ((char) (currentChar - 'A' + 13) % 26 + 'A');
                cryptText.append(currentChar);
            }

        }
        return cryptText.toString();

    }

    /**
     * Main method of the SecretCode class
     * 
     * @param args
     */
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        while (1 > 0) {
            System.out.println("Enter plain text to encode, or QUIT to end");
            Scanner keyboard = new Scanner(System.in);
            String plainText = keyboard.nextLine();
            if (plainText.equals("QUIT")) {
                break;
            }
            String cryptText = SecretCode.rotate13(plainText);
            String encodedText = SecretCode.rotate13(plainText);

            System.out.println("Encoded Text: " + encodedText);
        }

    }

}

Hello everyone, I am wanting this program to encode uppercase letters and leave the other characters alone and pass them through the output. For example "HELLO WORLD!" should become after running the program "URYY\ d_YQ!" and I am getting YLUHREYLYLBOWJJWBOERYLQDXK instead of "URYY\ d_YQ!" which is what I am suppose to get. If anyone can let me know what I did wrong I would greatly appreciate it. Thanks in advance.

Answer 1

It would be easier if you used String matching with regular expressions. First of all, in your loop condition, eliminate -1. Otherwise you're only getting to the second to last character.

Next, eliminate the cryptText.append(currentChar); before the if statement. Then, use this

char currentChar = plainText.charAt(i);
String cS = currentChar+"";
currentChar = (char) ((char) (currentChar - (int)'A' + 13) % 26 + (int)'A');

if (!cS.matches("[A-Z]")) {

    cryptText.append(plainText.charAt(i));
}
else {
    cryptText.append(currentChar);
}

This actually works, except that I'm getting some different characters from what you want. HELLO WORLD! => URYYB JBEYQ!