java编程实现一个HTTP服务器程序和HTTP客户端程序，使用线程池处理客户端请求

以下是一个简单的Java HTTP服务器程序和客户端程序实现，使用线程池来处理客户端请求：

HTTP服务器程序：

import java.io.*;
import java.net.*;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class HTTPServer {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(8000);
        ExecutorService pool = Executors.newCachedThreadPool();

        while (true) {
            Socket socket = serverSocket.accept();
            pool.execute(new RequestHandler(socket));
        }
    }
}

class RequestHandler implements Runnable {
    private final Socket socket;

    public RequestHandler(Socket socket) {
        this.socket = socket;
    }

    @Override
    public void run() {
        try {
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            DataOutputStream out = new DataOutputStream(socket.getOutputStream());

            String request = in.readLine();
            System.out.println("Request: " + request);

            out.writeBytes("HTTP/1.1 200 OK\r\n\r\n");
            out.writeBytes("Hello World!");

            in.close();
            out.close();
            socket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

HTTP客户端程序：

import java.io.*;
import java.net.*;
import java.util.Scanner;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class HTTPClient {
    public static void main(String[] args) throws IOException {
        Scanner scanner = new Scanner(System.in);
        ExecutorService pool = Executors.newCachedThreadPool();

        while (true) {
            System.out.print("Enter URL (or 'exit' to quit): ");
            String input = scanner.nextLine();

            if (input.equals("exit")) {
                break;
            }

            URL url = new URL(input);
            pool.execute(new RequestHandler(url));
        }

        scanner.close();
    }
}

class RequestHandler implements Runnable {
    private final URL url;

    public RequestHandler(URL url) {
        this.url = url;
    }

    @Override
    public void run() {
        try {
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");

            BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            String line;

            while ((line = in.readLine()) != null) {
                System.out.println(line);
            }

            in.close();
            connection.disconnect();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

在这个示例中，服务器监听端口8000并使用线程池来处理客户端请求。每当一个客户端连接到服务器时，服务器会为其分配一个线程来处理请求。当客户端发送HTTP GET请求时，服务器将返回“Hello World!”消息。

客户端程序允许用户输入URL并使用线程池来发送HTTP GET请求。每个请求也会分配一个线程来处理响应。响应将被打印到控制台上。