curl command equivalent in java

Here is my curl command:

curl https://login.xyz.com/v1/oauth/token -H "Accept:
application/json" --data 'client_id=client_id' --data
'client_secret=client_secret' --data 'redirect_uri=redirect_uri'
--data 'code=code'

I'm trying to post that in java. Here is what i was trying to do:

String resourceUrl = "https://login.xyz.com/v1/oauth/token?client_id=<client.id>&client_secret=<client.secret>&redirect_uri=https://login.xyz.com/user/login&code=<code>";
HttpURLConnection httpcon = (HttpURLConnection) ((new URL(resourceUrl).openConnection()));
httpcon.setDoOutput(true);
httpcon.setRequestProperty("Content-Type", "application/json");
httpcon.setRequestProperty("Accept", "application/json");
httpcon.setRequestMethod("POST");
httpcon.connect();      
System.out.println(httpcon.getHeaderField(0));

But I'm getting HTTP/1.1 500 Internal Server Error