I’m not an expert on the HTTP protocol, but from what I can remember don’t need to send the ? as part of the request.
Also, if the back end is yours, you might want to take a look at what you are receiving there. Maybe this can give you a clue as to what goes wrong. I doubt though, that it’s a bug in the URL library as it’s part of the java std-lib and therefor get’s used by millions of programs.