java简单聊天室

import java.awt.*;
import java.applet.*;
import java.awt.event.*;
import javax.swing.*;
public class Applet1 extends Applet implements ActionListener,ItemListener
{
  TextArea mainText;
    JTextField input;
    JButton sendButton,disconnectButton,connectButton;
    Checkbox secretCheck;
    Choice objChoice;
 String name="大家";
 public void init()
   { 
   mainText=new TextArea("",10,15);
  
  
      input=new  JTextField("",40);
      sendButton=new JButton("发送");
      sendButton.setForeground(Color.blue);
     
      disconnectButton=new JButton("断开连接");
      disconnectButton.setForeground(Color.blue);
      connectButton=new JButton("连接主机");
      connectButton.setForeground(Color.blue);
      secretCheck=new Checkbox("密谈");
      objChoice=new Choice();
   objChoice.add("大家");
      objChoice.add("little girl");
      objChoice.add("boy");
    this.setBackground(new Color(200,210,50));
    add(new ChatPanel());
 sendButton.addActionListener(this);
 objChoice.addItemListener(this);
   }
   public void actionPerformed(ActionEvent e)
 {
      
    mainText.append("你对"+name+"说:"+input.getText()+"\n");
    input.setText("");
    
       
 }
   public void itemStateChanged(ItemEvent e)
 {
       name=(String)e.getItem();
 }
class ChatPa