Java实现客户端与服务器的聊天

要实现Java客户端与服务器的聊天，可以使用Socket套接字来建立通信连接。下面是一个简单的示例代码：

服务端：

import java.net.*;
import java.io.*;

public class Server {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = null;
        try {
            serverSocket = new ServerSocket(8888);
        } catch (IOException e) {
            System.err.println("Could not listen on port: 8888.");
            System.exit(1);
        }

        Socket clientSocket = null;
        try {
            clientSocket = serverSocket.accept();
        } catch (IOException e) {
            System.err.println("Accept failed.");
            System.exit(1);
        }

        PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
        BufferedReader in = new BufferedReader(
                new InputStreamReader(
                        clientSocket.getInputStream()));

        String inputLine, outputLine;
        while ((inputLine = in.readLine()) != null) {
            outputLine = "Server: " + inputLine;
            out.println(outputLine);
            if (outputLine.equals("Server: Bye."))
                break;
        }
        out.close();
        in.close();
        clientSocket.close();
        serverSocket.close();
    }
}

客户端：

import java.io.*;
import java.net.*;

public class Client {
    public static void main(String[] args) throws IOException {
        Socket clientSocket = null;
        PrintWriter out = null;
        BufferedReader in = null;

        try {
            clientSocket = new Socket("localhost", 8888);
            out = new PrintWriter(clientSocket.getOutputStream(), true);
            in = new BufferedReader(new InputStreamReader(
                                        clientSocket.getInputStream()));
        } catch (UnknownHostException e) {
            System.err.println("Don't know about host: localhost.");
            System.exit(1);
        } catch (IOException e) {
            System.err.println("Couldn't get I/O for "
                               + "the connection to: localhost.");
            System.exit(1);
        }

        BufferedReader stdIn = new BufferedReader(
                                   new InputStreamReader(System.in));
        String userInput;
        while ((userInput = stdIn.readLine()) != null) {
            out.println(userInput);
            System.out.println("Server says: " + in.readLine());
            if (userInput.equals("Bye."))
                break;
        }

        out.close();
        in.close();
        stdIn.close();
        clientSocket.close();
    }
}

以上代码中，服务端创建一个ServerSocket实例并绑定到指定的端口，等待客户端连接。客户端创建一个Socket实例并连接到服务端。客户端和服务端都可以通过输入和输出流来发送和接收数据。在示例中，客户端从标准输入读取用户输入并发送到服务端，服务端接收到数据后将其转发回客户端。当客户端发送“Bye.”时，程序结束通信。