code: private static String byteToHexString(byte[] bytes)
    {
      final char[] hexArray = "0123456789ABCDEF".toCharArray();
      char[] hexChars = new char[bytes.length * 2];
      for (int j = 0; j < bytes.length; j++)
      {
        int v = bytes[j] & 0xFF;
        hexChars[j * 2] = hexArray[v >>> 4];
        hexChars[j * 2 + 1] = hexArray[v & 0x0F];
      }
      return new String(hexChars);
    }
docs: Converts Byte array to hex string
  
  @param bytes a byte array
  @return a string in hexadecimal code