JAVA 接口与回调 初学者笔记

package timer;

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.time.Instant;

public class TimerTest
{  
   public static void main(String[] args)
   {  
      var listener = new TimePrinter();//构造一个监听器

    
      var timer = new Timer(1000, listener);//一个定时器（）中前为计时间隔毫秒，后为传入的对象
      timer.start();//启动定时

      // keep program running until the user selects "OK"
      JOptionPane.showMessageDialog(null, "Quit program?");
      System.exit(0);
   }
}

class TimePrinter implements ActionListener
{  
   public void actionPerformed(ActionEvent event)
   {  
      System.out.println("At the tone, the time is " 
         + Instant.ofEpochMilli(event.getWhen()/*会返回这个事件的时间*/));
      Toolkit.getDefaultToolkit().beep();//获取工具箱（工具箱中包含GUI环境信息）并发出一声铃响
   }
}