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🌐 java.net — Networking — HTTP client, URL, sockets (Java 11+)

The modern java.net.http.HttpClient (Java 11+) provides a clean synchronous and asynchronous HTTP/2 client. The older java.net.URL class is still widely used for simple requests.

Import: import java.net.*; | Docs: Oracle JavaDoc

📋 Classes, Methods & Constants

Name	Signature	Description
HttpClient	class HttpClient (java.net.http)	Modern HTTP/1.1 and HTTP/2 client (Java 11+)
HttpClient.newHttpClient	static HttpClient newHttpClient()	Create default HTTP client
HttpClient.newBuilder	static Builder newBuilder()	Build HTTP client with custom settings
HttpRequest	class HttpRequest (java.net.http)	Immutable HTTP request
HttpRequest.newBuilder	static Builder newBuilder(URI uri)	Build HTTP request
request.GET	Builder GET()	Set method to GET
request.POST	Builder POST(BodyPublisher body)	Set method to POST with body
BodyPublishers.ofString	static BodyPublisher ofString(String body)	Create request body from string
HttpResponse	class HttpResponse<T> (java.net.http)	HTTP response with body
response.statusCode	int statusCode()	Return HTTP status code
response.body	T body()	Return response body
response.headers	HttpHeaders headers()	Return response headers
client.send	HttpResponse<T> send(HttpRequest req, BodyHandler<T> handler)	Synchronous send
client.sendAsync	CompletableFuture<HttpResponse<T>> sendAsync(...)	Asynchronous send
BodyHandlers.ofString	static BodyHandler<String> ofString()	Receive body as String
URI.create	static URI create(String str)	Create URI from string
URL	class URL (java.net)	Legacy URL class
url.openStream	InputStream openStream() throws IOException	Open connection and return InputStream

💡 Example Program

Save as ClassName.java (matching the public class name), compile with javac ClassName.java, run with java ClassName.

import java.net.URI;
import java.net.http.*;
import java.net.http.HttpResponse.BodyHandlers;
import java.time.Duration;

public class JavaNetDemo {
    public static void main(String[] args) throws Exception {
        HttpClient client = HttpClient.newBuilder()
            .connectTimeout(Duration.ofSeconds(10))
            .build();

        // --- GET request ---
        HttpRequest getReq = HttpRequest.newBuilder()
            .uri(URI.create("https://jsonplaceholder.typicode.com/posts/1"))
            .header("Accept", "application/json")
            .GET()
            .build();

        HttpResponse<String> resp = client.send(getReq, BodyHandlers.ofString());
        System.out.println("Status : " + resp.statusCode());
        System.out.println("Body   : " + resp.body().substring(0, 120) + "...");

        // --- POST request ---
        String json = "{\"title\":\"Go Reference\",\"body\":\"MyWebUniversity\",\"userId\":1}";
        HttpRequest postReq = HttpRequest.newBuilder()
            .uri(URI.create("https://jsonplaceholder.typicode.com/posts"))
            .header("Content-Type", "application/json")
            .POST(HttpRequest.BodyPublishers.ofString(json))
            .build();

        HttpResponse<String> postResp = client.send(postReq, BodyHandlers.ofString());
        System.out.println("\nPOST status: " + postResp.statusCode());
        System.out.println("POST body  : " + postResp.body());

        // --- Check response headers ---
        postResp.headers().map().forEach((k, v) ->
            System.out.printf("  Header: %-25s = %s%n", k, v));
    }
}
// javac JavaNetDemo.java && java JavaNetDemo
// (requires internet connection)

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