Java HTTPUrlConnection returns 500 status code

I'm trying to GET a url using HTTPUrlConnection, however I'm always getting a 500 code, but when I try to access that same url from the browser or using curl, it works fine!

This is the code

try{
    URL url = new URL("theurl"); 
    HttpURLConnection httpcon = (HttpURLConnection) url.openConnection();
    httpcon.setRequestProperty("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8");
    httpcon.setRequestProperty("User-Agent", "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:14.0) Gecko/20100101 Firefox/14.0.1");
    System.out.println(httpcon.getHeaderFields());
    }catch (Exception e) {
        System.out.println("exception "+e);
    }

When I print the headerfields, it shows the 500 code.. when I change the URL to something else like google.com , it works fine. But I don't understand why it doesn't work here but it works fine on the browser and with curl.

Any help would be highly appreciated..

Thank you,