做好的Java聊天室怎么加登录功能，代码如下

这代码是直接进入聊天室的，我想新建一个login类用登录窗口进行登录，有哪位会的帮我写一下，万分感谢
public class Client extends JFrame implements Runnable,ActionListener,WindowListener{

private Container contentPane;//顶级容器
private JLabel label;//标签，显示名字
private JTextArea msgContext;//显示聊天内容
private MyChoice list;//在线列表
private JTextField msg;//要聊天的信息
private String userName;//用户名
private String title;//客户端标题
private Socket socket;//
private BufferedReader read;//读
private PrintWriter write;//写
private Panel p;//面板
private ScrollPane scroll;//滚动条
public Client(String title,String userName)
{
super(title);
this.userName=userName;
inIt();
go();
}
public void inIt()//初始化
{
try {
socket=new Socket("127.0.0.1",7778);
write=new PrintWriter(new OutputStreamWriter(socket.getOutputStream()),true);
read=new BufferedReader(new InputStreamReader(socket.getInputStream()));
write.println(userName+":上线了");
} catch (Exception e) {
e.printStackTrace();
}
contentPane=getContentPane();
contentPane.setLayout(new BorderLayout());

label=new JLabel(userName);
msgContext=new JTextArea(20,45);
msgContext.setEditable(false);//设置为不可编辑
msg=new JTextField(16);
msg.addActionListener(this);
list=new MyChoice();
p=new Panel();
scroll=new ScrollPane(ScrollPane.SCROLLBARS_ALWAYS);

contentPane.add(label,BorderLayout.NORTH);
p.add(msgContext);
scroll.add(p);
contentPane.add(scroll,BorderLayout.CENTER);
contentPane.add(msg,BorderLayout.SOUTH);
contentPane.add(list,BorderLayout.EAST);
list.addActionListener(this);
this.addWindowListener(this);
setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
setBounds(200, 200, 600, 400);
new Thread(this).start();
}
public void go()//跑起来
{
this.setVisible(true);
this.validate();
}
public static void main(String[] args) {
// TODO Auto-generated method stub
/**
* 注意：客户端不能取相同的名字，否则会出错
*/
Client client=new Client("chat","che");
Client client1=new Client("chat","yan");
Client client2=new Client("chat","bing"); 就把这三个用户改成用登录界面登录的。

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