CyclicBarrier循环栅栏

CyclicBarrier循环栅栏

1.概念

CountDownLatch不能重用,每次循环必须创建新的对象.

CyclicBarrier 循环栅栏，用来进行线程协作，等待线程满足某个计数。
构造时设置『计数个数』，每个线程执行到某个需要“同步”的时刻调用 await() 方法进行等待，当等待的线程数满足『计数个数』时，继续执行 .

CyclicBarrier 与 CountDownLatch 的主要区别在于 CyclicBarrier 是可以重用的 CyclicBarrier 可以被比喻为『人满发车』

1.CyclicBarrier基本用法

package com.concurrent.p10;

import lombok.extern.slf4j.Slf4j;
import org.junit.Test;

import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

@Slf4j(topic = "c.Test_CyclicBarrier")
public class Test_CyclicBarrier {
    
    

    public void sleep(long mills) {
    
    
        try {
    
    
            Thread.sleep(mills);
        } catch (InterruptedException e) {
    
    
            e.printStackTrace();
        }
    }

    /**
     * 输出:
     *16:24:52.761 [pool-1-thread-2] DEBUG c.Test_CyclicBarrier - task2 stat...
     * 16:24:52.761 [pool-1-thread-1] DEBUG c.Test_CyclicBarrier - task1 stat...
     * 16:24:55.766 [pool-1-thread-2] DEBUG c.Test_CyclicBarrier - task1,task2 finish...
     * 16:24:55.766 [pool-1-thread-2] DEBUG c.Test_CyclicBarrier - task2 end...
     * 16:24:55.766 [pool-1-thread-1] DEBUG c.Test_CyclicBarrier - task1 end...
     * 16:24:55.766 [pool-1-thread-1] DEBUG c.Test_CyclicBarrier - task2 stat...
     * 16:24:55.766 [pool-1-thread-2] DEBUG c.Test_CyclicBarrier - task1 stat...
     * 16:24:58.766 [pool-1-thread-1] DEBUG c.Test_CyclicBarrier - task1,task2 finish...
     * 16:24:58.766 [pool-1-thread-2] DEBUG c.Test_CyclicBarrier - task1 end...
     * 16:24:58.766 [pool-1-thread-2] DEBUG c.Test_CyclicBarrier - task1 stat...
     * 16:24:58.766 [pool-1-thread-1] DEBUG c.Test_CyclicBarrier - task2 end...
     * 16:24:58.766 [pool-1-thread-1] DEBUG c.Test_CyclicBarrier - task2 stat...
     * 16:25:01.766 [pool-1-thread-1] DEBUG c.Test_CyclicBarrier - task1,task2 finish...
     * 16:25:01.766 [pool-1-thread-2] DEBUG c.Test_CyclicBarrier - task1 end...
     * 16:25:01.766 [pool-1-thread-1] DEBUG c.Test_CyclicBarrier - task2 end...
     */
    @Test
    public void test1() {
    
    
        //创建线程池
        ExecutorService service = Executors.newFixedThreadPool(2);
        //创建CyclicBarrier
        CyclicBarrier cyclicBarrier = new CyclicBarrier(2, () -> {
    
    
            log.debug("task1,task2 finish...");
        });

        for (int i = 0; i < 3; i++) {
    
    
            service.submit(() -> {
    
    
                log.debug("task1 stat...");
                sleep(2000);
                try {
    
    
                    cyclicBarrier.await();  //2-1=1
                } catch (InterruptedException | BrokenBarrierException e) {
    
    
                    e.printStackTrace();
                }
                log.debug("task1 end...");
            });

            service.submit(() -> {
    
    
                log.debug("task2 stat...");
                sleep(3000);
                try {
    
    
                    cyclicBarrier.await();  //1-1=0
                } catch (InterruptedException | BrokenBarrierException e) {
    
    
                    e.printStackTrace();
                }
                log.debug("task2 end...");
            });
        }
        service.shutdown();
        for (; ; ) ;
    }
}