在Android Studio中使用Java从url获取JSON？

<uses-permission android:name="android.permission.INTERNET" />

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class JsonFetcher {
    public static String fetchJsonFromUrl(String urlString) {
        try {
            URL url = new URL(urlString);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");
            connection.connect();

            int responseCode = connection.getResponseCode();
            if (responseCode == HttpURLConnection.HTTP_OK) {
                InputStream inputStream = connection.getInputStream();
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
                StringBuilder stringBuilder = new StringBuilder();
                String line;
                while ((line = bufferedReader.readLine()) != null) {
                    stringBuilder.append(line).append("\n");
                }
                bufferedReader.close();
                return stringBuilder.toString();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

        return null;
    }
}

import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {
    private static final String JSON_URL = "https://example.com/api/data.json";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        new JsonTask().execute(JSON_URL);
    }

    private class JsonTask extends AsyncTask<String, Void, String> {
        @Override
        protected String doInBackground(String... urls) {
            return JsonFetcher.fetchJsonFromUrl(urls[0]);
        }

        @Override
        protected void onPostExecute(String jsonString) {
            // 在这里处理获取到的JSON数据
        }
    }
}