An example of how to make a GET request in Java then using the GSON library to format the response data (JSON).

GetRequest.java

import java.net.URL;
import java.util.HashMap;
import java.io.IOException;
import java.io.InputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.reflect.TypeToken;

public class GetRequest {

	static String URL = "";  // Set this as required.
	static String METHOD = "GET";
	static String AUTH_STRING = ""; // Set this as required or comment it out.
	
	static String getResponse(InputStream stream) throws IOException {
		String buffer;
		StringBuffer response = new StringBuffer();
		BufferedReader res = new BufferedReader(new InputStreamReader(stream));	
		while ((buffer = res.readLine()) != null)
			response.append(buffer);
		return response.toString();
	}
	
	static void prettyPrint(String response) {
		Gson gson = new GsonBuilder().setPrettyPrinting().create();
		HashMap<String, Object> thing = gson.fromJson(response, new TypeToken<HashMap<String, Object>>(){}.getType());
		System.out.println(gson.toJson(thing));
	}
	
	public static void main(String args[]) {
		URL url;
		try {
			String response;
			url = new URL(GetRequest.URL);
			HttpURLConnection conn = (HttpURLConnection)url.openConnection();
			conn.setRequestMethod(GetRequest.METHOD);
			conn.setDoOutput(false);
			conn.setRequestProperty("Authorization", GetRequest.AUTH_STRING);
			System.out.println("Response Code: " + conn.getResponseCode());
			if (conn.getResponseCode() != 200)
				response = GetRequest.getResponse(conn.getErrorStream());
			else
				response = GetRequest.getResponse(conn.getInputStream());
			System.out.println("Response Body: " + response);
			GetRequest.prettyPrint(response);
		}
		catch (MalformedURLException e) {e.printStackTrace();}
		catch (IOException e) {e.printStackTrace();}  
	}
	
}