CountDownLatch
使用原理
-
创建CountDownLatch并设置计数器值。
-
启动多线程并且调用CountDownLatch实例的countDown()方法。
-
主线程调用
await()方法，这样主线程的操作就会在这个方法上阻塞，直到其他线程完成各自的任务，count值为0，停止阻塞，主线程继续执行。
使用模板
public class CountDownLatchTest {
/**
* a start signal that prevents any worker from proceeding
* until the driver is ready for them to proceed;
* @param args
* @throws InterruptedException
*/
public static void main(String[] args) throws InterruptedException {
CountDownLatch startSignal = new CountDownLatch(1);
CountDownLatch doneSignal = new CountDownLatch(10);
for (int i = 0; i < 10; i++) {
// create and start threads
new Thread(new Worker(startSignal, doneSignal)).start();
}
// don't let run yet
System.out.println("do something else 1");
// let all threads proceed
startSignal.countDown();
System.out.println("do something else 2");
// wait for all to finish
doneSignal.await();
System.out.println("wait for all to finsh");
}
static class Worker implements Runnable{
private final CountDownLatch startSignal;
private final CountDownLatch doneSignal;
Worker(CountDownLatch startSignal, CountDownLatch doneSignal) {
this.startSignal = startSignal;
this.doneSignal = doneSignal;
}
@Override
public void run() {
try {
startSignal.await();
doWork();
doneSignal.countDown();
} catch (InterruptedException ex) {
ex.printStackTrace();
}
}
void doWork() {
System.out.println("do work!");
}
}
}