public static String combine(String h1,String h2) {
        int length = (h1.length() > h2.length()) ? h2.length() : h1.length();
        StringBuilder builder = new StringBuilder();

        for (int i =0 ; i<length; i+=2) {
            String output = h1.substring(i, (i + 2));
            String output2 = h2.substring(i, (i + 2));


            int decimal = Integer.parseInt(output, 16);
            int decimal2 = Integer.parseInt(output2, 16);


            int result = decimal ^ decimal2;
            builder.append(result + " ");
        }

        return builder.toString();
    }