CyclicBarrier 用法，汇总统计

原创于 2022-08-30 17:54:39 发布 · 233 阅读

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本文介绍了一个使用Java实现的多线程程序，该程序通过创建固定数量的线程池来并行地添加整数到一个共享列表中，并最终计算这些整数的总和。为确保数据的一致性和线程安全，程序采用了CyclicBarrier和ReentrantLock。

package net.biancheng.c.thread;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.locks.ReentrantLock;

/**
 * @author cheng
 * @Description 统计所有线程的数字汇总
 * @Date 2022/8/29 17:29
 */
public class Caculate {
    public static  List<Integer> list = new ArrayList<Integer>();

    public static void main(String[] args) {
        int nums = 15;
        ExecutorService executor = Executors.newFixedThreadPool(nums);
        CyclicBarrier barrier = new CyclicBarrier(nums, () -> {
            try {
                System.out.println("Arrays.toString(list.toArray()) = " + Arrays.toString(list.toArray()));
                Integer total = 0;
                for (int i = 0; i < list.size(); i++) {
                    total = total + list.get(i);
                }
                System.out.println("total = " + total);

            } catch (Exception e) {
                e.printStackTrace();
            }

        });

        for (int i = 0; i < nums; i++) {
            executor.submit(new Each(barrier, (i + 1)));
        }

        executor.shutdown();
    }

    static class Each implements Runnable {
        private CyclicBarrier barrier;
        private Integer nums;
        private static final ReentrantLock lock = new ReentrantLock();

        public Each(CyclicBarrier barrier, Integer nums) {
            this.barrier = barrier;
            this.nums = nums;
        }

        @Override
        public String toString() {
            return "Each{" +
                    "barrier=" + barrier +
                    ", nums=" + nums +
                    '}';
        }

        @Override
        public void run() {

            try {
                //必须同步,不然nums可能为空;
              /*  synchronized(Each.class){
                    list.add(nums);
                }*/
                lock.lock();
                list.add(nums);
                lock.unlock();
                System.out.println(Thread.currentThread().getName() + ",nums = " + nums);
                barrier.await();
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (BrokenBarrierException e) {
                e.printStackTrace();
            }
        }
    }

}