Queue 阻塞队列 DelayQueue

Posted 2022-06-14 han6

package com.dh.learn.queue;

import java.util.concurrent.DelayQueue;
import java.util.concurrent.Delayed;
import java.util.concurrent.TimeUnit;

public class LearnDelayQueue 
    // DelayQueue 只能放置实现了Delayed接口的元素  底层使用的是PriorityQueue
    //1. 在put时加了ReentrantLock，保证线程安全，由于是无界队列，在put时不会发生阻塞
    //2. 在take时，根据每个Delayed元素的延时，利用Condition去await对应的时间，直到Delayed元素的延时为0时，就可以取出元素了。

    public static void main(String[] args) 
        DelayQueue<MyDelay> delayQueue = new DelayQueue<>();
        delayQueue.put(new MyDelay("111"));
        delayQueue.put(new MyDelay("222"));
        delayQueue.put(new MyDelay("333"));
        delayQueue.put(new MyDelay("444"));

        System.out.println("开始时间" + System.currentTimeMillis());
        try 
            delayQueue.take();
         catch (InterruptedException e) 
            e.printStackTrace();
        
        System.out.println("结束时间" + System.currentTimeMillis());
    

    static class MyDelay implements Delayed 
        private String name;
        private long start = System.currentTimeMillis();
        private long time;

        public MyDelay(String name) 
            this.name = name;
            //1s的延时
            this.time = 1000;
        

        @Override
        public long getDelay(TimeUnit unit) 
            return unit.convert((start + time) -
                    System.currentTimeMillis(), TimeUnit.MILLISECONDS);
        

        @Override
        public int compareTo(Delayed o) 
            return 0;
        

        @Override
        public String toString() 
            return super.toString();