java多线程组件二:DelayQueue的使用方法

本篇文章主要用来介绍DeleyQueue的使用方式,根据这个类的名字就可以判断,这是一个Queue,且从它里面去的元素的顺序是按照时间的延迟来的.网上有很多例子,可是都不是很详细,我把书上的例子看了一下,然后用自己的思路写出来,原来发现里面还是有很多的误区,下面的程序是例子,加了一些注释:

/** *  */package com.eric.concurrency;import java.util.ArrayList;import java.util.List;import java.util.Random;import java.util.concurrent.DelayQueue;import java.util.concurrent.Delayed;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.TimeUnit;/** * this class used to explain how to use delayqueue * @author Eric *  */public class DelayQueueDemo {public static void main(String[] args) {try {ExecutorService es = Executors.newCachedThreadPool();DelayQueue<DelayTask> queue = new DelayQueue<DelayTask>();Random rand = new Random();// add 20's DelayTask to DelayQueuefor (int i = 0; i < 20; i++) {queue.add(new DelayTask(rand.nextInt(500)));}EndTask endTaks = new EndTask(501);// add endtask to DelayQueue, it's time is 50001 to ensure will be// execute at the end of queuequeue.add(endTaks);es.execute(new DelayConsumer(queue));TimeUnit.SECONDS.sleep(1);es.shutdownNow();} catch (InterruptedException e) {e.printStackTrace();}}}class DelayConsumer implements Runnable {private DelayQueue<DelayTask>queue;public DelayConsumer(DelayQueue<DelayTask> queue) {this.queue = queue;}public void run() {try {System.out.println("############print order by DelayQueue###############");// from DelayQueue get DelayTask and execute itwhile (!Thread.interrupted()) {queue.take().run();}} catch (InterruptedException e) {System.out.println("Exit Consumer");}}}class EndTask extends DelayTask {public EndTask(long delay) {super(delay);}@Overridepublic void run() {try {TimeUnit.MILLISECONDS.sleep(1);// print all task from internal listSystem.out.println("#############print by list order###############");for (DelayTask delayTask : tasks) {System.out.println("end" + delayTask);}} catch (InterruptedException e) {System.out.println("Exit LIST");}}}class DelayTask implements Runnable, Delayed {protected static List<DelayTask>tasks= new ArrayList<DelayTask>();public long                     time  = 0;public long                     delay;private static int             count  = 0;private int                     id      = count++;public DelayTask(long delay) {this.delay = delay;time = System.nanoTime() + TimeUnit.NANOSECONDS.convert(this.delay, TimeUnit.MICROSECONDS);tasks.add(this);}@Overridepublic int compareTo(Delayed o) {long result = ((DelayTask) o).getTime() - this.getTime();if (result > 0) {return 1;}if (result < 0) {return -1;}return 0;}@Overridepublic long getDelay(TimeUnit unit) {return unit.convert(time - System.nanoTime(), TimeUnit.NANOSECONDS);}@Overridepublic void run() {System.out.println(this);}public String toString() {// use time to print for get real "delay time"return "Task " + id + ":" + time;}public long getTime() {return time;}public void setTime(long time) {this.time = time;}}

这个程序运行的结果分两部分,一部分是从QUEUE中取出来的元素,另一部分是从普通的链表里拿出来的展示的结果.所有的元素按照相同的顺序分别放到queue和list中,最后展现的顺序是不同的,在list中的元素是按照放入的顺序取出的,而DelayQueue中的元素是按照Delay的delay因素来决定取出的顺序