code: static String toHexString(byte[] data) {
      char[] chArray = new char[data.length * 2];
      int pos = 0;
      for (byte b : data) {
        chArray[pos++] = HEX_CHARS[(b >> 4) & 0x0f];
        chArray[pos++] = HEX_CHARS[b & 0x0f];
      }
      return new String(chArray);
    }
docs: Convert byte array to a "hexa"-string.
  @param data Byte array to convert.
  @return "Hexa-string" representation.