code: public static String getMD5Checksum(Resource res) throws Exception {
  	byte[] b = createChecksum(res);
  	String result = "";
  	for (int i = 0; i < b.length; i++) {
  	    result += Integer.toString((b[i] & 0xff) + 0x100, 16).substring(1);
  	}
  	return result;
      }
docs: a byte array to a HEX string