java 多线程 计时器

package s6;

import java.awt.BorderLayout;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.Calendar;
import java.util.Date;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;

public class Countdown {
private JFrame frame;
private JLabel labeltime;

public Countdown(){
frame=new JFrame("倒\t计\t时\t器");
labeltime=new JLabel();
init();
addEventHandler();
}

private void init(){
frame.setLayout(new BorderLayout());
frame.add(labeltime,BorderLayout.CENTER);
}

private void showMe(){
frame.setSize(400,300);