code: private static String byteArrayToHexString(byte[] bytes) {
          StringBuilder sb = new StringBuilder(bytes.length * 2);
          for (byte element : bytes) {
              int v = element & 0xff;
              if (v < 16) {
                  sb.append('0');
              }
              sb.append(Integer.toHexString(v));
          }
          return sb.toString();
      }
docs: Using some super basic byte array &lt;-&gt; hex conversions so we don't
  have to rely on any large Base64 libraries. Can be overridden if you
  like!
  
  @param bytes byte array to be converted
  @return string containing hex values