利用runnable接口和Thread类 创建一个数字时钟小程序

import javax.swing.*;
import java.awt.*;
import java.lang.*;
import java.util.*;
public class ClockTest extends JFrame{
ClockPane clockPane;

public ClockTest()
{
setTitle("Clock Program");
clockPane=new ClockPane();
//JPanel pane=new JPanel();
//pane.setLayout(new GridLayout(1,1,16,16));
//pane.add(clockPane);

setContentPane(clockPane);
}

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
ClockTest test=new ClockTest();
test.pack();
test.setVisible(true);
}
}
class ClockPane extends JPanel
implements Runnable{
Thread thread;

public ClockPane(){
if(thread==null)
{
thread=new Thread(this);
thread.start();
}
}
@Override
public void run() {
// TODO Auto-generated method stub
while(true)
{
repaint();
try{
Thread.sleep(1000);

}
catch(Exception e)
{

}
}

}
@Override
protected void paintComponent(Graphics arg0) {
// TODO Auto-generated method stub
Graphics2D comp2D=(Graphics2D)arg0;
//comp2D.setBackground(Color.black);
//comp2D.fillRect(0, 0, getSize().width, getSize().height);
//comp2D.setFont(new Font("浪漫雅园",Font.BOLD,15));
comp2D.clearRect(0, 0, 666, 550);
comp2D.setColor(Color.RED);
Calendar cal=Calendar.getInstance();
comp2D.drawString(cal.getTime().toString(), 10, 50);

}

}