Java多线程 定时器

Posted 2021-03-10

Java多线程中的定时器（java.util.Timer）有定时执行任务的功能，通过设定定时器的间隔时间，会自动在此间隔后执行预先安排好的任务（java.util.TimerTask）。
timer.schedule(TimerTask,delay,interval time)
第一个参数是需要执行的任务。此类的类型为java.util.TimerTask。第二个参数是执行任务前等待时间，第三个参数是间隔时间（单位为毫秒）

package timer;

import java.util.concurrent.PriorityBlockingQueue;

public class MyTimer {
PriorityBlockingQueue<MyTimerTask> queue = new PriorityBlockingQueue<>();
Worker worker;

private static class Worker extends Thread {
    PriorityBlockingQueue<MyTimerTask> queue;

    Worker(PriorityBlockingQueue<MyTimerTask> queue) {
        this.queue = queue;
    }

    @Override
    public void run() {
        while (true) {
            try {
                MyTimerTask task = queue.take();
                long current = System.currentTimeMillis();
                if (task.delay <= current) {
                    task.target.run();
                } else {
                    queue.put(task);
                    Thread.sleep(task.delay - current);
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

MyTimer() {
    worker = new Worker(queue);
    worker.start();
}

void execute(Runnable target, long delay) {
    queue.put(new MyTimerTask(target, delay));
}

public static void main(String[] args) {
    MyTimer timer = new MyTimer();
    timer.execute(new Runnable() {
        @Override
        public void run() {
            System.out.println("该起床了");
        }
    }, 2000);
    System.out.println("另一个人");
}

}
package timer;

public class MyTimerTask implements Comparable<MyTimerTask> {
Runnable target;
long delay;

MyTimerTask(Runnable target, long delay) {
    this.target = target;
    this.delay = System.currentTimeMillis() + delay;//延时后的时刻

}

@Override
public int compareTo(MyTimerTask o) {
    if (delay == o.delay) {
//延时后的时刻
        return 0;
    } else if (delay < o.delay) {
        return -1;
    } else {
        return 1;
    }
}

}