用eclipse写一个简单聊天程序并给出代码

好的，下面是一个简单的聊天程序的示例代码。这个程序分为服务器端和客户端两部分，你需要在 Eclipse 中创建两个项目分别对应这两部分。

服务器端代码：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.text.SimpleDateFormat;
import java.util.Date;

public class Server {
    public static void main(String[] args) {
        try {
            ServerSocket server = new ServerSocket(8888);
            System.out.println("Server started. Waiting for clients...");
            Socket socket = server.accept();
            System.out.println("Client connected: " + socket.getInetAddress().getHostAddress());

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

            while (true) {
                String message = in.readLine();
                if (message == null) {
                    break;
                }
                System.out.println("Received message: " + message);

                // 获取当前时间
                SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
                String time = sdf.format(new Date());

                // 发送消息给客户端
                out.println(time + " Server: " + message);
            }

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

客户端代码：

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollBar;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.ScrollPaneConstants;

public class Client {
    private static final String SERVER_IP = "localhost";
    private static final int SERVER_PORT = 8888;

    private Socket socket;
    private BufferedReader in;
    private PrintWriter out;

    private JFrame frame;
    private JTextArea messageArea;
    private JTextField inputField;
    private JButton sendButton;

    public Client() {
        // 创建界面
        frame = new JFrame("Chat Room");
        JPanel panel = new JPanel(new BorderLayout());
        messageArea = new JTextArea();
        messageArea.setEditable(false);
        JScrollPane scrollPane = new JScrollPane(messageArea);
        scrollPane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
        panel.add(scrollPane, BorderLayout.CENTER);
        inputField = new JTextField();
        inputField.setPreferredSize(new Dimension(200, 30));
        sendButton = new JButton("Send");
        JPanel inputPanel = new JPanel(new BorderLayout());
        inputPanel.add(inputField, BorderLayout.CENTER);
        inputPanel.add(sendButton, BorderLayout.EAST);
        panel.add(inputPanel, BorderLayout.SOUTH);
        frame.setContentPane(panel);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();

        // 连接服务器
        try {
            socket = new Socket(SERVER_IP, SERVER_PORT);
            in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            out = new PrintWriter(socket.getOutputStream(), true);
        } catch (IOException e) {
            e.printStackTrace();
        }

        // 发送消息按钮的事件处理
        sendButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                String message = inputField.getText();
                if (!message.equals("")) {
                    out.println(message);
                    inputField.setText("");
                }
            }
        });

        // 接收消息的线程
        Thread receiveThread = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    while (true) {
                        String message = in.readLine();
                        if (message == null) {
                            break;
                        }
                        messageArea.append(message + "\n");

                        // 滚动到最底部
                        JScrollBar vertical = scrollPane.getVerticalScrollBar();
                        vertical.setValue(vertical.getMaximum());
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
        receiveThread.start();

        // 显示界面
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        new Client();
    }
}

这个示例程序中，服务器端和客户端之间的通信使用的是阻塞式的 IO。在实际的应用中，你可能需要使用非阻塞式的 IO 或者 NIO，以提高程序的并发性能和响应速度。同时，这个程序还有很多需要改进的地方，比如异常处理、UI 界面的美化等等。