java - java中哪里使用屏障模式？

Question

我刚刚阅读了有关 Phaser 的 javadoc there并对该类的使用有疑问。 javadoc 提供了一个示例，但是现实生活中的示例呢？这样的屏障实现在实践中可能有用吗？

Answer 1

我没有使用过Phaser，但我使用过CountDownLatch。引用的文档说:

[Phaser is] similar in functionality to ... CountDownLatch but supporting more flexible usage.

CountDownLatch 在您触发多个线程来执行某些任务的任何地方都很有用，在老式学校中，您会使用 Thread.join() 来等待它们完成。

<小时/>

例如:

老派:

Thread t1 = new Thread("one");
Thread t2 = new Thread("two");

t1.start();
t2.start();    

t1.join();
t2.join();
System.out.println("Both threads have finished");

使用CountDownLatch

public class MyRunnable implement Runnable {
    private final CountDownLatch c;  // Set this in constructor

    public void run() {
        try {
            // Do Stuff ....
        } finally {
            c.countDown();
        }
    }
}

<小时/>

CountDownLatch c = new CountDownLatch(2);

executorService.submit(new MyRunnable("one", c));
executorService.submit(new MyRunnable("two", c));

c.await();
System.out.println("Both threads have finished");