ConcurrentLinkedQueue 和CountDownLatch 的使用

ConcurrentLinkedQueue 和CountDownLatch 的使用

package com.chow.queue;import java.util.concurrent.ConcurrentLinkedQueue;import java.util.concurrent.CountDownLatch;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;/** * Created by zhouhaiming on 2017-5-26 17:22 * Email: [e-mail] * * @Description: */public class ConcurrentLinkedQueueTest {    private static ConcurrentLinkedQueue<Integer> queue = new ConcurrentLinkedQueue<Integer>();    private static int count = 2; // 线程个数    //CountDownLatch，一个同步辅助类，在完成一组正在其他线程中执行的操作之前，它允许一个或多个线程一直等待。    private static CountDownLatch latch = new CountDownLatch(count);    public static void main(String[] args) throws InterruptedException {        long timeStart = System.currentTimeMillis();        ExecutorService es = Executors.newFixedThreadPool(4);        ConcurrentLinkedQueueTest.offer();        for (int i = 0; i < count; i++) {            es.submit(new Poll());        }        latch.await(); //使得主线程(main)阻塞直到latch.countDown()为零才继续执行        System.out.println("cost time " + (System.currentTimeMillis() - timeStart) + "ms");        es.shutdown();    }    /**     * 生产     */    public static void offer() {        for (int i = 0; i < 5; i++) {            queue.offer(i);        }    }    /**     * 消费     */    static class Poll implements Runnable {        public void run() {            // while (queue.size()>0) {            while (!queue.isEmpty()) {                System.out.println(queue.poll());            }            latch.countDown();        }    }}/*运行结果：        costtime 2360ms        改用while (queue.size()>0)后        运行结果：        cost time 46422ms        结果居然相差那么大，看了下ConcurrentLinkedQueue的API原来.size()是要遍历一遍集合的，难怪那么慢，所以尽量要避免用size而改用isEmpty().*/