用Java编写聊天功能的代码

我很乐意回答你的问题。以下是一个简单的使用Java编写聊天功能的示例代码：

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

public class ChatServer {
    private ServerSocket server = null;
    private Socket client = null;
    private BufferedReader in = null;
    private PrintWriter out = null;

    public ChatServer(int port) {
        try {
            server = new ServerSocket(port);
            System.out.println("服务器启动成功，等待客户端连接...");

            client = server.accept();
            System.out.println("客户端连接成功！");

            in = new BufferedReader(new InputStreamReader(client.getInputStream()));
            out = new PrintWriter(client.getOutputStream(), true);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void start() {
        String msg = "";
        try {
            while ((msg = in.readLine()) != null) {
                System.out.println("客户端：" + msg);
                out.println("服务器："+ msg);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                in.close();
                out.close();
                client.close();
                server.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) {
        ChatServer server = new ChatServer(8888);
        server.start();
    }
}

这个代码演示了如何使用Java的Socket API来创建一个简单的服务器，使用BufferedReader和PrintWriter实现客户端与服务器之间的消息传输。你可以根据自己的需要对代码进行修改和扩展。