[java] Server returned HTTP response code: 400

I am trying to get an InputStream from a URL. The URL can be a opened from Firefox. It returns a json and I have installed an addon for viewing json in Firefox so I can view it there.

So I tried to get it from Java by:

URL url = new URL(urlString);
URLConnection urlConnection = url.openConnection();
BufferedReader reader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));

But it is throwing an IOException in urlConnection.getInputStream().

I also tried:

HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
InputStream inputStream = url.openStream();

But no luck.

Any information is appreciable. Thanks in advance.