Creating Ceasar Cipher in Java

Question

I'm currently working on a project in which I'm to create a Ceaser Cipher by taking a file as input and then requesting a number from the user. The number is to be used to shift letters forward, so if the number inputted was 2, a would become c. The alphabet is to wrap around (so if the letter is z and the input is 2, the ciphered letter would be b), and the program is to ignore non-letter characters and simply continue onward.

I've got a solution that I belive should work, but I think I'm missing something as the output is NOT what I expected nor what it should be. I've included the relevant section of code below

public static String encode(String content, int num){
    char[] contentArray = content.toCharArray();
    String encoded = "";
    for(int i = 0; i < contentArray.length; i++){
        char current = contentArray[i];
        if (current >= 'a' && current <='z' || current >= 'A' && current <= 'Z'){
            current = (char) (current + num);
            if (current > 'z' | current > 'Z'){
                current = (char) (current - 26);
            } else if (current < 'a' | current < 'A'){
                current = (char) (current + 26);
            }
            contentArray[i] = current;
            encoded = encoded + encoded.concat(Character.toString(contentArray[i]));
        } else {
            i++;
        }
    }
    return encoded;
}

Up above that is my main function, which simply asks the user for the necessary input before calling this function. In this case, the string content consists of the following characters: taco cat 1-349z 2

In theory, this should return vceq ecv 1-349b 2, if the user inputs 2 as num. Unfortunately that returns the following...

\I\IK\I\IKW\I\IK\I\IKWI\I\IK\I\IKW\I\IK\I\IKWI\\I\IK\I\IKW\I\IK\I\IKWI\I\IK\I\IKW\I\IK\I\IKWI\b

...which is obviously NOT correct. I have no idea what is going wrong in my code, so any assistance would be greatly appreciated. Thank you!

Answer 1

try this

public static String encode(String enc, int offset) {
        offset = offset % 26 + 26;
        StringBuilder encoded = new StringBuilder();
        for (char i : enc.toCharArray()) {
            if (Character.isLetter(i)) {
                if (Character.isUpperCase(i)) {
                    encoded.append((char) ('A' + (i - 'A' + offset) % 26));
                } else {
                    encoded.append((char) ('a' + (i - 'a' + offset) % 26));
                }
            } else {
                encoded.append(i);
            }
        }
        return encoded.toString();
    }

Usage

 System.out.println(encode("taco cat 1-349z", 2));