Question

I created this code that looks at a string token and formats it so that every character is moved along by one. The characters are all lowercase and from a to z.

So if my input is
abcz

Output is
bcda

Right now I added all the alphabets to an arraylist, and the code determines the index of each character and adds one to it. If it finds z, it prints a so that index of the arraylist is not out of range.

List<String> letters = new ArrayList<String>(); 
        String alp = "abcdefghijklmnopqrstuvwxyz";
        for (int i = 0; i<26; i++)
        {
            letters.add(Character.toString(alp.charAt(i)));
        }

        String token = sc.next();
        for (int i = 0; i<token.length(); i++)
        {
            if (letters.get(letters.indexOf(Character.toString(token.charAt(i)))).equals("z"))
            {
                System.out.print("a");
            }
            else
            {
            System.out.print(letters.get(letters.indexOf(Character.toString(token.charAt(i)))+1));
            }
        }

Answer 1

A simple loop with a bit of modular arithmetic will do, why bother with so many objects?

for(int i = 0; i < token.length(); ++i) {
    System.out.print(('a' + (token.charAt(i) + 1 - 'a')%('z' - 'a' + 1)));
}

We increase the offset from 'a' by one, and take the remainder modulo 26 to get an offset in the range from 0 to 25.