code: static private String convertByteArrToString(byte[] byteArr) {
      StringBuilder sb = new StringBuilder();
      for (byte b : byteArr) {
        int i = b;
        i = i & 0xff;
        sb.append(String.format("%02x", i));
      }
      return sb.toString();
    }
docs: Array of bytes to brute-force convert into a hexadecimal string.
  The length of the returned string is byteArr.length * 2.
  
  @param byteArr byte array to convert
  @return hexadecimal string