Java并发编程：CountDownLatch和CyclicBarrier的应用示例

原创阳光穿透心脏的1/2处 2024-11-07 06:12 19阅读 0赞

Java并发编程中，`CountDownLatch`和`CyclicBarrier`是两个常用的同步辅助类，它们可以帮助我们控制并发任务的执行顺序。下面我将分别给出`CountDownLatch`和`CyclicBarrier`的应用示例。

### CountDownLatch应用示例`CountDownLatch`是一个同步辅助类，在完成一组正在其他线程中执行的操作之前，它允许一个或多个线程一直等待。

```javaimport java.util.concurrent.CountDownLatch;

public class CountDownLatchExample {
 public static void main(String[] args) throws InterruptedException {
 final int threadCount =5;
CountDownLatch latch = new CountDownLatch(threadCount);

for (int i =0; i < threadCount; i++) {
 new Thread(new Worker(latch)).start();
 }

latch.await(); //等待所有线程完成 System.out.println("所有任务完成");
 }

static class Worker implements Runnable {
 private final CountDownLatch latch;

public Worker(CountDownLatch latch) {
 this.latch = latch;
 }

@Override public void run() {
 try {
 System.out.println(Thread.currentThread().getName() + "正在执行任务");
//模拟任务执行时间Thread.sleep(1000);
 System.out.println(Thread.currentThread().getName() + "任务完成");
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
 latch.countDown(); //任务完成，计数减1 }
 }
 }
}
```### CyclicBarrier应用示例`CyclicBarrier`是一个同步辅助类，它允许一组线程相互等待，直到所有线程都到达某个公共屏障点（barrier point）。

```javaimport java.util.concurrent.CyclicBarrier;
import java.util.concurrent.TimeUnit;

public class CyclicBarrierExample {
 public static void main(String[] args) throws InterruptedException {
 final int threadCount =5;
CyclicBarrier barrier = new CyclicBarrier(threadCount, new Runnable() {
@Override public void run() {
 System.out.println("所有线程已到达屏障点，继续执行");
 }
 });

for (int i =0; i < threadCount; i++) {
 new Thread(new Worker(barrier)).start();
 }
 }

static class Worker implements Runnable {
 private final CyclicBarrier barrier;

public Worker(CyclicBarrier barrier) {
 this.barrier = barrier;
 }

@Override public void run() {
 try {
 System.out.println(Thread.currentThread().getName() + "正在执行任务");
//模拟任务执行时间Thread.sleep((long) (Math.random() *1000));
 System.out.println(Thread.currentThread().getName() + "到达屏障点，等待其他线程");
 barrier.await(); //等待其他线程到达屏障点 System.out.println(Thread.currentThread().getName() + "继续执行任务");
} catch (Exception e) {
e.printStackTrace();
 }
 }
 }
}
```在这两个示例中，`CountDownLatch`用于确保主线程等待所有工作线程完成，而`CyclicBarrier`用于让所有工作线程在某个点上相互等待，然后一起继续执行。这两个工具类在处理复杂的并发问题时非常有用。