怎么用java写个倒计时？

import javax.swing.*;

public class Test extends JFrame
{
JButton button;
JPanel panel;
Test1DaoJiShi2()
{
super("10秒计数器");
button=new JButton();
panel=new JPanel();
add(panel);
panel.add(button);

setSize(300,200);
setVisible(true);

ButtonAction tt=new ButtonAction();
tt.run();

}

class ButtonAction extends Thread
{
int i=10;
public void run() //线程在此开始执行
{
while(i!=0)
{
try
{
sleep(1000);
button.setText( "还有 " +i+ "秒 ");
i--;
}
catch(Exception eee)
{}
}

if(i==0)
{
JOptionPane.showMessageDialog(null, " 时间到！");
}
}
}

public static void main(String args[])
{
JFrame frm = new Test();
frm.dispose();
System.exit(0);
}
}