这个聊天室系统JAVA的代码请编写

好的，请先确保你已经安装了JDK和Eclipse等必要的开发工具。下面是一个简单的聊天室系统的Java代码示例，包括客户端和服务器端：

服务器端代码：

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;

public class ChatServer {
    private static final int PORT = 8888;
    private List<ClientHandler> clients = new ArrayList<ClientHandler>();

    public ChatServer() {
        ServerSocket server = null;
        try {
            server = new ServerSocket(PORT);
            System.out.println("Server started on port " + PORT);
            while (true) {
                Socket client = server.accept();
                ClientHandler handler = new ClientHandler(client);
                clients.add(handler);
                new Thread(handler).start();
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (server != null) {
                try {
                    server.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    public synchronized void broadcast(String message) {
        for (ClientHandler client : clients) {
            client.sendMessage(message);
        }
    }

    public synchronized void removeClient(ClientHandler client) {
        clients.remove(client);
    }

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

    class ClientHandler implements Runnable {
        private Socket client;
        private String username;
        private ChatServer server;

        public ClientHandler(Socket client) {
            this.client = client;
            this.server = ChatServer.this;
        }

        public void run() {
            try {
                username = Utils.receiveMessage(client);
                server.broadcast(username + " has joined the chat.");
                while (true) {
                    String message = Utils.receiveMessage(client);
                    server.broadcast(username + ": " + message);
                }
            } catch (IOException e) {
                System.out.println(username + " has left the chat.");
            } finally {
                server.removeClient(this);
                Utils.close(client);
            }
        }

        public void sendMessage(String message) {
            Utils.sendMessage(client, message);
        }
    }
}

客户端代码：

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import java.net.Socket;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

public class ChatClient {
    private static final String SERVER_HOST = "localhost";
    private static final int SERVER_PORT = 8888;

    private Socket socket;
    private String username;

    private JTextArea messageArea;
    private JTextField inputField;

    public ChatClient() {
        try {
            socket = new Socket(SERVER_HOST, SERVER_PORT);
            username = showLoginDialog();
            if (username == null) {
                Utils.close(socket);
                return;
            }
            System.out.println("Connected to server " + SERVER_HOST + ":" + SERVER_PORT + " as " + username);
            showChatFrame();
            new Thread(new ServerHandler()).start();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private String showLoginDialog() {
        // TODO: show login dialog and return username
        return "test";
    }

    private void showChatFrame() {
        JFrame frame = new JFrame("Chat Room");
        frame.setSize(600, 400);
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        messageArea = new JTextArea();
        messageArea.setLineWrap(true);
        messageArea.setEditable(false);
        messageArea.setFont(new Font("Arial", Font.PLAIN, 14));

        JScrollPane scrollPane = new JScrollPane(messageArea);
        scrollPane.setBorder(BorderFactory.createTitledBorder("Message"));

        inputField = new JTextField();
        inputField.setFont(new Font("Arial", Font.PLAIN, 14));

        JButton sendButton = new JButton("Send");
        sendButton.setFont(new Font("Arial", Font.PLAIN, 14));
        sendButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String message = inputField.getText().trim();
                if (!message.equals("")) {
                    Utils.sendMessage(socket, message);
                    inputField.setText("");
                }
            }
        });

        JPanel inputPanel = new JPanel(new BorderLayout());
        inputPanel.setBorder(BorderFactory.createTitledBorder("Input"));
        inputPanel.add(inputField, BorderLayout.CENTER);
        inputPanel.add(sendButton, BorderLayout.EAST);

        frame.add(scrollPane, BorderLayout.CENTER);
        frame.add(inputPanel, BorderLayout.SOUTH);
        frame.setVisible(true);
    }

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

    class ServerHandler implements Runnable {
        public void run() {
            try {
                while (true) {
                    String message = Utils.receiveMessage(socket);
                    messageArea.append(message + "\n");
                }
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                Utils.close(socket);
            }
        }
    }
}

以上代码仅供参考，需要根据实际情况进行修改和完善。实现一个完整的聊天室系统需要考虑更多的细节和功能，比如用户登录、退出、私聊、文件传输等，建议你在实践中逐步完善。