code: private static String bytesToHex(byte[] bytes) {
          char[] hexChars = new char[bytes.length * 2];
          for (int i = 0; i < bytes.length; i++) {
              int v = bytes[i] & 0xFF;
              hexChars[i * 2] = hexArray[v >>> 4];
              hexChars[i * 2 + 1] = hexArray[v & 0x0F];
          }
          return new String(hexChars);
      }
docs: We don't have Guava here