JsonTask

@SuppressLint("StaticFieldLeak")
private class JsonTask extends AsyncTask<String, String, String> {

    private HttpURLConnection connection = null;
    private BufferedReader reader = null;

    protected String doInBackground(String... params) {
        try {
            URL url = new URL(params[0]);
            connection = (HttpURLConnection) url.openConnection();
            connection.connect();

            InputStream stream = connection.getInputStream();
            reader = new BufferedReader(new InputStreamReader(stream));

            StringBuilder builder = new StringBuilder();
            String line;
            while ((line = reader.readLine()) != null && !isCancelled()) {
                builder.append(line).append("\n");
            }
            return builder.toString();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (connection != null) {
                connection.disconnect();
            }
            try {
                if (reader != null) {
                    reader.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return null;
    }

    @Override
    protected void onPostExecute(String json) {
        Log.d("TAG", json);
    }
}

Copy the class content and put it inside MainActivity but not inside a method. Invoke like this: new JsonTask().execute("HTTPS_URL_TO_JSON_DATA");, e.g. in a button click handler in onCreate(). onPostExecute(String json) will be automatically invoked with the json result.