java考研倒计时

截止日期2021年12月25日零点
代码借鉴了教科书

import javax.swing.*;
import java.awt.*;
import java.util.Calendar;
import java.util.GregorianCalendar;

public class Timerframe {
    private Jframe jf;
    private JLabel label1;
    private JLabel label2;

    public Timerframe() {
        jf = new Jframe("倒计时牌");
        label1 = new JLabel("距离考研");
        label2 = new JLabel(" ");
        jf.add(label1, BorderLayout.NORTH);
        jf.add(label2, BorderLayout.CENTER);
        GregorianCalendar deadline = new GregorianCalendar();
        deadline.set(2021,11,25,0,0,0);
        Thread t = new RefreshTimeThread(deadline);
        t.start();
    }
        public void showMe(){
            jf.setBounds(200,200,300,150);
            jf.setVisible(true);
            jf.setDefaultCloseOperation(Jframe.EXIT_ON_CLOSE);
        }

    public static void main(String[] args) {
        new Timerframe().showMe();
    }
    class RefreshTimeThread extends Thread{
        private Calendar targetTime;
        public RefreshTimeThread(Calendar targetTime){
            this.targetTime=targetTime;
        }
        @Override
        public  void  run(){
            while(true){
                Calendar todayTime=new GregorianCalendar();
                System.out.println(todayTime.getTime());
                long seconds=(targetTime.getTimeInMillis()-todayTime.getTimeInMillis())/1000;
                if(seconds<=0){
                    label2.setText("时间到");
                    break;
                }
                int day=(int)(seconds/(24*60*60));
                int hour=(int) (seconds/(60*60)%24);
                int min=(int)(seconds/60%60);
                int sec=(int)(seconds%60);
                String str=day+"天"+hour+"时"+min+"分"+sec+"秒";
                label2.setText(str);
                try{
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}