关于java多用户在线聊天程序的有关问题。

import java.net.*;
import java.net.*;
import java.io.*;
public class Server{
    private final int maxClientCount = 10;
    private int clientNum = 0;
    private ServerSocket ss;
    private ChatThread communicationThread[];
    public Server(){
        //创建ServerSocket,允许10人在线
        try{
            ss = new ServerSocket(10000,maxClientCount);
        }
        catch(IOException e){
            System.err.println(e.toString());
            System.exit(1);
        }
        
        communicationThread = new ChatThread[maxClientCount];
        //循环等待用户连接
        for(int i=0;i<maxClientCount;i++){
            try{
                communicationThread[i] = new ChatThread(ss.accept(),i);    //连接成功时启动它
                communicationThread[i].start();
                clientNum++;
            }
            catch(IOException e){
                System.err.println(e.toString());
                System.exit(1);
            }
        }
    }
    //线程类
    private class ChatThread extends Thread{   
        private Socket socket;
        private int clientID;
        private DataInputStream br;
        private DataOutputStream bw;
        public ChatThread(Socket socket,int number){
            this.socket = socket;
            clientID = number;
            try{
                //从socket获得输入流和输出流
                br = new DataInputStream(socket.getInputStream());
                bw = new DataOutputStream(socket.getOutputStream());
            }
            catch(IOException e){
                System.err.println(e.toString());
                System.exit(1);
            }
        }
        //run()方法
        public void run(){
            try{
                bw.writeInt(clientID);
            }
            catch(IOException e){
                System.err.println(e.toString());
                System.exit(1);
            }
            //循环读一用户的信息，并把它发送给其他用户
            while(true){
                try{
                    //读对应的用户发送过来的信息
                    String message = br.readUTF();
                    //发送给其他用户
                    for(int i=0;i<clientNum;i++){
                        communicationThread[i].bw.writeUTF("客户" + clientID + ":" + message);
                    }
                    if(message != null && message.equals("bye"))
                        break;
                }
                catch(IOException e){
                    System.err.println(e.toString());
                    System.exit(1);
                }
            }
            try{
                bw.close();
                br.close();
                socket.close();
            }
            catch(EOFException e){
                System.err.println(e.toString());
            }
            catch(IOException e){
                System.err.println(e.toString());
            }
        }
    }
    
    
    public static void main(String args[]){
        new Server();
    }
}

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


public class Client extends JFrame implements Runnable{
    private int clientID;
    private String clientWord;
    private JPanel topPanel;
    private JLabel nameLabel;
    private JTextField wordField;
    private JButton submit;
    private JTextArea displayField;
    private Socket socket;
    private DataInputStream br;
    private DataOutputStream bw;
    //构造面板
    public Client(){
        Container container = getContentPane();
        container.setLayout(new BorderLayout(5,5));
        topPanel = new JPanel(new FlowLayout());
        nameLabel = new JLabel("");
        wordField = new JTextField(20);
        submit = new JButton("发送");
        submit.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent event){
                try{
                    String sentence = wordField.getText();
                    bw.writeUTF(sentence);
                }
                catch(IOException e){
                    System.err.println(e.toString());
                }
            }
        });
        topPanel.add(nameLabel);
        topPanel.add(wordField);
        topPanel.add(submit);
        displayField = new JTextArea();
        container.add(topPanel,BorderLayout.NORTH);
        container.add(displayField,BorderLayout.CENTER);
        setSize(400,500);
        setResizable(false);
        setVisible(true);
    }
    //主方法
    public static void main(String args[]){
        Client clientWindow = new Client();
        clientWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        clientWindow.nor();
    }
    //创建线程和socket连接
    public void nor(){
        Thread commThread = new Thread(this);
        commThread.start();
        try{
            socket = new Socket("127.0.0.1",10000);
            br = new DataInputStream(socket.getInputStream());
            bw = new DataOutputStream(socket.getOutputStream());
        }
        catch(IOException e){
            System.err.println(e.toString());
        }
    }
    //run方法
    public void run(){
        try{
            //设置Label的文本
            clientID = br.readInt();
            SwingUtilities.invokeLater(new Runnable(){
                public void run(){
                    nameLabel.setText("客户" + clientID);
                }
            });
            //循环读服务端发来的信息
            while(true){
                clientWord = br.readUTF();
                displayMessage(clientWord);
            }
        }
        catch(EOFException e){
            System.err.println(e.toString());
        }
        catch(IOException e){
            System.err.println(e.toString());
        }
    }
    //把信息显示出来
    private void displayMessage(final String message){
        SwingUtilities.invokeLater(new Runnable(){
            public void run(){
                displayField.append(message + "\n");
                displayField.setCaretPosition(displayField.getText().length());
            }
        });
    }
}