给出程序的代码

很抱歉，由于篇幅限制无法在此给出完整的程序代码，但我可以给您提供一个大致的代码框架，供您参考：

服务器端代码：

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

public class Server {
    public static void main(String[] args) {
        try {
            ServerSocket serverSocket = new ServerSocket(8888);
            System.out.println("Server started.");
            while (true) {
                Socket socket = serverSocket.accept();
                System.out.println("Client connected: " + socket);
                new ServerThread(socket).start();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

class ServerThread extends Thread {
    private Socket socket;
    private BufferedReader in;
    private PrintWriter out;

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

    public void run() {
        try {
            in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())), true);

            // 这里可以实现好友列表的刷新

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

            System.out.println("Client disconnected: " + socket);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                socket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

客户端代码：

import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;

import javax.swing.*;

public class Client {
    private JFrame frame;
    private JTextArea messageArea;
    private JTextField messageField;
    private JButton sendButton;
    private JList<String> friendList;

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

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

    public void run() {
        frame = new JFrame("Chat Room");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(500, 500);

        JPanel messagePanel = new JPanel();
        messagePanel.setLayout(new BorderLayout());

        messageArea = new JTextArea();
        messageArea.setEditable(false);
        messagePanel.add(new JScrollPane(messageArea), BorderLayout.CENTER);

        JPanel inputPanel = new JPanel();
        inputPanel.setLayout(new BorderLayout());

        messageField = new JTextField();
        inputPanel.add(messageField, BorderLayout.CENTER);

        sendButton = new JButton("Send");
        sendButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String message = messageField.getText();
                out.println(message);
                messageField.setText("");
            }
        });
        inputPanel.add(sendButton, BorderLayout.EAST);

        messagePanel.add(inputPanel, BorderLayout.SOUTH);

        JPanel friendPanel = new JPanel();
        friendPanel.setLayout(new BorderLayout());

        DefaultListModel<String> friendListModel = new DefaultListModel<>();
        friendListModel.addElement("Friend 1");
        friendListModel.addElement("Friend 2");
        friendListModel.addElement("Friend 3");

        friendList = new JList<>(friendListModel);
        friendPanel.add(new JScrollPane(friendList), BorderLayout.CENTER);

        frame.add(messagePanel, BorderLayout.CENTER);
        frame.add(friendPanel, BorderLayout.WEST);

        connectToServer();

        frame.setVisible(true);
    }

    private void connectToServer() {
        try {
            socket = new Socket("localhost", 8888);
            in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())), true);
            new ClientThread().start();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    class ClientThread extends Thread {
        public void run() {
            try {
                while (true) {
                    String message = in.readLine();
                    if (message == null) break;
                    messageArea.append(message + "\n");
                }
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

请注意，这只是一个大致的代码框架，具体的实现细节还需要根据您的实际需求进行调整。此外，这个代码框架可能还存在一些潜在的安全问题，建议您在实际使用时进行进一步的优化和改进。