Java 多线程系列 CountDownLatch

CountDownLatch

一个或多个线程等待其他线程完成操作后在在执行

CountDownLatch通过一个计数器来实现,await方法阻塞直到 countDown() 调用计数器归零之后释放所有等待的线程,并且任何后续的await调用立即返回。这是一次性现象 - 计数无法重置。如果您需要重置计数的版本,请考虑使用CyclicBarrier。


public class WorkerRunnable implements Runnable { private CountDownLatch countDownLatch;
private int i; public WorkerRunnable(CountDownLatch latch, int i) {
this.countDownLatch = latch;
this.i = i;
} @Override
public void run() {
doWork();
this.countDownLatch.countDown();
} private void doWork() {
System.out.println("当前的线程: " + i);
}
} public class Client { public static void main(String[] args) throws InterruptedException {
final int n = 10;
CountDownLatch doneSignal = new CountDownLatch(n);
ExecutorService executor = Executors.newFixedThreadPool(10); for (int i = 0; i < n; i++) {
executor.execute(new WorkerRunnable(doneSignal, i));
} doneSignal.await();
System.out.println("结束");
}
}

out

当前的线程: 7
当前的线程: 6
当前的线程: 2
当前的线程: 1
当前的线程: 9
当前的线程: 0
当前的线程: 5
当前的线程: 4
当前的线程: 8
当前的线程: 3
结束
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