CountDownLatch 简单学习

最新推荐文章于 2023-12-25 21:49:44 发布

原创最新推荐文章于 2023-12-25 21:49:44 发布 · 174 阅读

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本文探讨了如何使用并发编程技术计算一组人员跑步的总时间，并通过CountDownLatch和CyclicBarrier实现任务间的同步与等待。文章详细介绍了如何利用Java并发库中的组件来优化并行执行效率。

import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.Callable;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.FutureTask;
import java.util.concurrent.atomic.AtomicInteger;

public class TestCountDownLatch {
    private static List<String>  mans      = new ArrayList<String>();
    private static CyclicBarrier barrier   = null;
    private static AtomicInteger costTimes = new AtomicInteger(0);

    static {
        mans.add("andy");
        mans.add("jack");
        mans.add("lili");
        mans.add("alan");
        mans.add("bill");
        //barrier = new CyclicBarrier(mans.size() + 1);
    }

    public static class Walk implements Runnable {
        private AtomicInteger  ct = new AtomicInteger(0);
        private String         name;
        private CountDownLatch latch;

        public Walk(String name, AtomicInteger countTime, CountDownLatch cdl) {
            ct = countTime;
            this.name = name;
            //            latch = cdl;
        }

        @Override
        public void run() {
            int walkTime = new Random().nextInt(20);
            try {
                if ("lili".equals(name)) {
                    Thread.sleep(10000);
                } else
                    Thread.sleep(1000);
            } catch (InterruptedException e) {

            }
            System.out.println(name + " walk " + walkTime + "min");

            // ct.addAndGet(walkTime);
            //            try {
            //                // barrier.await();
            //                latch.countDown();
            //            } catch (Exception e) {
            //
            //            }

            System.out.println(name + " walk over!");
            System.out.println("all person walk " + ct.addAndGet(walkTime));
        }

    }

    public static class Walk1 implements Callable<Integer> {
        private String name;

        public Walk1(String n) {
            this.name = n;
        }

        @Override
        public Integer call() {
            int walkTime = new Random().nextInt(20);
            try {
                if ("lili".equals(name)) {
                    Thread.sleep(10000);
                } else
                    Thread.sleep(1000);
            } catch (InterruptedException e) {

            }
            System.out.println(name + " walk " + walkTime + "min");
            return walkTime;
        }

    }

    public static void main(String[] args) throws Exception {
        //        try {
        //            CountDownLatch latch = new CountDownLatch(mans.size());
        //            ExecutorService es = Executors.newFixedThreadPool(mans.size());
        //            for (String str : mans) {
        //                es.submit(new Walk(str, costTimes, latch));
        //            }
        //
        //            es.shutdown();
        //            // latch.await();
        //            //barrier.await();
        //            System.out.println("TOTAL COST:" + costTimes + "min");
        //        } catch (Exception e) {
        //            System.out.println(e.getMessage());
        //        } finally {
        //
        //        }

        List<Future<Integer>> tasks = new ArrayList<Future<Integer>>();
        ExecutorService es = Executors.newFixedThreadPool(mans.size());
        for (String str : mans) {
            Walk1 w = new Walk1(str);
            FutureTask<Integer> f = new FutureTask<Integer>(w);
            tasks.add(f);
            es.submit(f);
        }

        es.shutdown();
        Integer costTimes = 0;
        for (Future<Integer> f : tasks) {
            costTimes += f.get();
        }

        System.out.println("TOTAL COST:" + costTimes + "min");
    }
}