Transform hex string to byte array

hexStringToByteArray.java

//  Transform hexadecimal String example
    public byte[] hexStringToByteArray(String s) {
        byte[] data;
        int len = s.length();
        data = new byte[len / 2];
        for (int i = 0; i < len; i += 2) {
            data[i / 2] = (byte) ((Character.digit( s.charAt( i ), 16 ) << 4)
                    + Character.digit( s.charAt( i + 1 ), 16 ));
        }
        return data;
    }