class Hex {

    public static String u4(int v) {
        char[] result = new char[8];
        for (int i = 0; i < 8; i++) {
            result[7 - i] = Character.forDigit(v & 0x0f, 16);
            v >>= 4;
        }

        return new String(result);
    }

    private  Hex();

}