Question

我希望我的主线程等到多个线程中的一个发出信号\ complete。

我不需要等待所有人发出信号\结束，只有一个。

完成此类要求的最佳做法是什么？

Answer 1

CountDownLatch会做你想要的。将其初始化为1并等待。 countDown()上的第一个线程将允许等待线程继续。

public class CountDownLatchTest
{
   public static void main(String[] args) throws InterruptedException {
      CountDownLatch gate = new CountDownLatch( 1 );
      for( int i = 0; i < 3; i++ ) {
         new Thread( new RandomWait( gate, i ) ).start();
      }
      gate.await();
      System.out.println("Done");
   }

   private static class RandomWait implements Runnable
   {
      CountDownLatch gate;
      int num;
      public RandomWait( CountDownLatch gate, int num )
      {
         this.gate = gate;
         this.num = num;
      }

      public void run() {
         try {
            Thread.sleep( (int)(Math.random() * 1000) );
            System.out.println("Thread ready: "+num);
            gate.countDown();
         } catch( InterruptedException ex ) {
         }
      }
   }
}

Answer 2

你做这样的事情

boolean complete=false;
Object waitSync = new Object();


 // the waiter has something like this

void waitFor() {
    synchronized (waitSync) {
        try {
            while (!complete)
                waitSync.wait();
        } catch (Exception e) {}
    }
}

// each worker calls something like this when completed

            synchronized (waitSync) {
            complete = true;
            waitSync.notifyAll();
        }

Answer 3

更简单的Condition接口可以。作为额外的奖励，您可以使用 Lock.newCondition（）

选择锁定

CountdownLatch只能发布一次，因此可能是您想要的，也可能不是。

另请参阅：Put one thread to sleep until a condition is resolved in another thread

等待主线程，直到Java中的多个线程信号之一

3 个答案: