并发编程JUC系列AQS(CountDownLatch、CyclicBarrier、Semaphore)

时间:2021-12-29 16:58:03

一、CountDownLatch

package com.jonychen.test;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * 并发编程java.util.concurrent(JUC)
 * AQS(AbstractQueuedSynchronizer)
 */
public class JUCAQSDemo {
    public static void main(String[] args){
/** * CountDownLatch用来控制一个线程等待多个线程,维护一个计数器cnt,
* 每次调用countDown()会让计数器的值减一, 减到零时,
* 那些因为调用await()方法而在等待的线程会被唤醒
*/
final int totalThread=10; CountDownLatch countDownLatch =new CountDownLatch(totalThread); ExecutorService executorService =Executors.newCachedThreadPool(); for (int i = 0; i < totalThread; i++) { executorService.execute(()->{ System.out.println("jonychen run"); countDownLatch.countDown(); }); } try { countDownLatch.await(); System.out.println("end..."); executorService.shutdown(); } catch (InterruptedException e) { e.printStackTrace(); } } }

运行截图:

并发编程JUC系列AQS(CountDownLatch、CyclicBarrier、Semaphore)

 

 

二、CyclicBarrier

 1 package com.jonychen.thread;
 2 
 3 import java.util.concurrent.BrokenBarrierException;
 4 import java.util.concurrent.CyclicBarrier;
 5 import java.util.concurrent.ExecutorService;
 6 import java.util.concurrent.Executors;
 7 
 8 /**
 9  * 并发编程java.util.concurrent(JUC)
10  * AQS(AbstractQueuedSynchronizer)
11  */
12 public class JUCAQSCycliBarrier {
13 /**
14 *CyclicBarrier用来控制多个线程相互等待,只有当多个线程都到达时,这些线程才会继续执行, 15 * 和CountDownLatch相似,都是通过维护计数器实现的,但他的计数器是递增的。每次执行await() 16 * 方法后,计数器会加1,直到计数器的值和设置的值相同,等待的所有线程才会继续执行,和CountDownLatch 17 * 的另一个区别是,CyclicBarrier的计数器可以循环使用,所以才叫他循环屏障 18   */
19     public static void main(String[] args){
20         final int totalThread=10;
21         CyclicBarrier cyclicBarrier =new CyclicBarrier(totalThread);
22         ExecutorService executorService=Executors.newCachedThreadPool();
23         for (int i = 0; i < totalThread; i++) {
24             executorService.execute(()->{
25                 System.out.println("before..*");
26                 try {
27                     cyclicBarrier.await();
28                 } catch (InterruptedException e) {
29                     e.printStackTrace();
30                 } catch (BrokenBarrierException e) {
31                     e.printStackTrace();
32                 }
33                 System.out.print("after   ");
34             });
35         }
36         executorService.shutdown();
37     }
38 }

运行截图:

并发编程JUC系列AQS(CountDownLatch、CyclicBarrier、Semaphore)

 

 

三、Semaphore

 

package com.jonychen.thread;

import sun.misc.Cleaner;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;

/**
 * 并发编程java.util.concurrent(JUC)
 * AQS(AbstractQueuedSynchronizer)
 */
public class JUCAQSSemaphore {

    public static void main(String[] args){
        /** *Semaphore就是操作系统中的信号量,可以控制对互斥资源的访问线程数 *以下代码模拟了对某个服务的并发请求,每次只能有30个客户端同时访问,请求总数为 10。 */
        final int clientCount=30;
        final int totalRequestCount=10;
        Semaphore semaphore =new Semaphore(clientCount);
        ExecutorService executorService=Executors.newCachedThreadPool();
        for (int i = 0; i < totalRequestCount; i++) {
            executorService.execute(()->{
                try {
                    semaphore.acquire();
                    System.out.println(semaphore.availablePermits() + "");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }finally {
                    semaphore.release();
                }
            });
        }
        executorService.shutdown();
    }
}

运行截图:

并发编程JUC系列AQS(CountDownLatch、CyclicBarrier、Semaphore)