Shift character in Alphabet

Question

Possible Duplicate:
ROT-13 function in java?

I have to shift all char from a string 13 places in the alphabet

private static String encode(String line) {
    char[] toEncode = line.toCharArray();
    for (int i = 0; i < toEncode.length; i++) {
        if (Character.isLetter(toEncode[i])) {
            toEncode[i] += 13;
        }
    }
    line = String.valueOf(toEncode);
    return line;
}

The Problem is that for example 'z' get to a ?. How can I solve that?

Thx for help.

Solution

It is because next chars after 'z' is punctuation chars and so on. You can shift so that 'z' will be 'n' for example.

toEncode[i] = (toEncode[i] + 13 - (int)'a') % 26 + (int)'a';

Comments

[Jayan]

@ Chandra Sekhar : Thanks for the answer: Please add explanations and guiding instructions for 'homework' questions .

[cottonman]

I know that this thread has been on here for quite some time now but I thought it would be worth posting this anyway for future reference. I think that you have a typo in your formula. Should it not be ...% 26... instead of 25 ? Since we want 'z' to shift to 'a' and not to 'b'.

[pepyakin]

Oh, yes, you are right. I'm mistakingly assumed that is alphabet consists of 25 letters.