import java.net.*;
import java.io.*;
public class HttpURLConnectionExample {
    private static HttpURLConnection con;
    public static void main(String[] args) throws Exception {
        URL url = new URL("https://www.example.com");
        con = (HttpURLConnection) url.openConnection();
        con.setRequestMethod("GET");
        BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
        String inputLine;
        StringBuffer content = new StringBuffer();
        while ((inputLine = in.readLine()) != null) {
            content.append(inputLine);
        }
        in.close();
        con.disconnect();
        System.out.println(content.toString());
    }
}

import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
public class HttpClientExample {
    public static void main(String[] args) throws Exception {
        CloseableHttpClient httpclient = HttpClients.createDefault();
        HttpGet httpget = new HttpGet("https://www.example.com");
        CloseableHttpResponse response = httpclient.execute(httpget);
        try {
            HttpEntity entity = response.getEntity();
            String result = EntityUtils.toString(entity);
            EntityUtils.consume(entity);
            System.out.println(result);
        } finally {
            response.close();
        }
    }
}

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
import java.io.IOException;
public class OkhttpExample {
    private static final OkHttpClient client = new OkHttpClient();
    public static void main(String[] args) throws IOException {
        Request request = new Request.builder()
        	.url("https://www.example.com")
        	.build();
        try (Response response = client.newCall(request).execute()) {
            String result = response.body().string();
            System.out.println(result);
        }
    }
}

public class HttpTemplate {
    public static String httpGet(String url) {
        RestTemplate restTemplate = new RestTemplate();
        String result = restTemplate.exchange(url, HttpMethod.GET, null, String.class).getBody();
        return result;
    }
    public static String httpPost(String url, String name) {
        RestTemplate restTemplate = new RestTemplate();
        return restTemplate.postForEntity(url, name, String.class).getBody();
    }
    public static void main(String str[]) {
        System.out.println(HttpTemplate.httpGet("https://www.example.com"));
        System.out.println(HttpTemplate.httpPost("https://www.example.com", "ming"));
    }
}