ROT decoder/encoder

ROTCipher.java

public class ROTCipher {
    private static final String ALPHABET = "abcdefghijklmnopqrstuvwxyz";
    public static String encode(String text,int rotations){
        String rotated = rotate(rotations);
        rotated += rotated.toUpperCase();
        String alphabet = ALPHABET + ALPHABET.toUpperCase();
        StringBuilder sb = new StringBuilder();
        for (char c : text.toCharArray()) {
            String s = c + "";
            if (s == " ")
                sb.append(" ");
            else if (!alphabet.contains(s))
                sb.append(s);
            else{
                sb.append(rotated.toCharArray()[alphabet.indexOf(c)]);
            }
        }
        return sb.toString();
    }
    public static String decode(String text,int rotations){
        String rotated = rotate(rotations);
        rotated += rotated.toUpperCase();
        String alphabet = ALPHABET + ALPHABET.toUpperCase();
        StringBuilder sb = new StringBuilder();
        for (char c : text.toCharArray()) {
            String s = c + "";
            if (s == " ")
                sb.append(" ");
            else if (!alphabet.contains(s))
                sb.append(s);
            else{
                sb.append(alphabet.toCharArray()[rotated.indexOf(c)]);
            }
        }
        return sb.toString();
    }
    private static String rotate(int rotations){
        String ret = ALPHABET;
        for (int i = 0; i < rotations; i++) {
            String s = ret.charAt(0) + "";
            ret = ret.substring(1);
            ret += s;
        }
        return ret;
    }
}

I like it