async doInBackground for JSON

gistfile1.txt

 @Override
        protected String doInBackground(String... strings) {
            try {
                URL mUrl = new URL(strings[0]);
                HttpURLConnection httpConnection = (HttpURLConnection) mUrl.openConnection();
                httpConnection.setRequestMethod("GET");
                httpConnection.setUseCaches(false);
                httpConnection.setAllowUserInteraction(false);
                httpConnection.connect();

                int responseCode = httpConnection.getResponseCode();

                if(responseCode == HttpURLConnection.HTTP_OK){
                    BufferedReader br = new BufferedReader(new InputStreamReader(httpConnection.getInputStream()));
                    StringBuilder sb = new StringBuilder();
                    String line;
                    while ((line = br.readLine()) != null) {
                        sb.append(line).append("\n");
                    }
                    br.close();
                    return sb.toString();
                }else
                    return null;
            } catch (IOException e) {
                e.printStackTrace();
            }
            return null;
        }