Java【多线程】定时器

Java标准库的定时器

import java.util.Timer;
import java.util.TimerTask;public class Test {public static void main(String[] args) {Timer timer = new Timer();timer.schedule(new TimerTask() {@Overridepublic void run() {System.out.println("hello timer");}},2000);System.out.println("hello main");}
}

正常描述任务，是Runnable

在定时器这里特殊一点，把Runnable封装了一下TimerTask

核心还是重写run方法

和线程池一样，timer中也包含前台线程阻止进程结束

实现定时器

1.创建一个类，表示一个任务

2.定时器中，能够管理多个任务的

必须使用一些集合类把这多个任务管理起来

3.实现schedule方法

把任务添加到队列即可

4.额外创建一个线程，负责执行队列中的任务

import java.util.PriorityQueue;class MyTimerTask implements Comparable<MyTimerTask>{private Runnable task;private long time;public MyTimerTask(Runnable task,long time) {this.task = task;this.time = time;}@Overridepublic int compareTo(MyTimerTask o) {return (int) (this.time-o.time);}public long getTime(){return time;}public void run(){task.run();}
}
class MyTimer {private PriorityQueue<MyTimerTask> queue = new PriorityQueue<>();private Object locker = new Object();public void schedule(Runnable task,long delay){synchronized (locker){MyTimerTask timerTask = new MyTimerTask(task,System.currentTimeMillis()+delay);queue.offer(timerTask);locker.notify();}}public MyTimer() {Thread t = new Thread(()->{try {while (true){synchronized (locker){while(queue.isEmpty()){locker.wait();}MyTimerTask task = queue.peek();if(task.getTime() > System.currentTimeMillis()){locker.wait(task.getTime()-System.currentTimeMillis());}else {task.run();queue.poll();}}}} catch (InterruptedException e) {throw new RuntimeException(e);}});t.start();}
}
public class Test2 {public static void main(String[] args) {MyTimer timer = new MyTimer();timer.schedule(new Runnable() {@Overridepublic void run() {System.out.println("hello");}},1000);}
}