多线程等待任务结束的几种方法
作者:互联网
比如,主线程创建线程池,提交n个任务,想让主线程在任务全部结束之后再继续做其他的事情。
1、使用awaitTermination方法
public static void main(String[] args) {
ExecutorService executor = Executors.newFixedThreadPool(3);
int i = 0;
AtomicInteger result = new AtomicInteger(0);
while (i < 10) {
i++;
executor.execute(() -> {
//每执行一次,对result加1
System.out.println(result.addAndGet(1));
});
}
System.out.println("调用shutdown()方法时,result的值为:" + result.get());
executor.shutdown();
try {
//等待所有任务结束,最多等待30分钟
executor.awaitTermination(30, TimeUnit.MINUTES);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("计算完成,result的值为:" + result.get() + ",可以继续处理其他事情了");
}
boolean awaitTermination(long timeout, TimeUnit unit)的作用:
Blocks until all tasks have completed execution after a shutdown request,
or the timeout occurs, or the current thread is interrupted,
whichever happens first.
2、借助工具类CountDownLatch
public static void main(String[] args) {
ExecutorService executor = Executors.newFixedThreadPool(3);
CountDownLatch latch = new CountDownLatch(10);
AtomicInteger result = new AtomicInteger(0);
for (int i = 1; i <= 10; i++) {
executor.execute(() -> {
//do something...
System.out.println(result.addAndGet(1));
//then
latch.countDown();
});
}
System.out.println("调用shutdown()方法时,result的值为:" + result.get());
executor.shutdown();
try {
latch.await();//等待任务结束:其实是等待latch值为0
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("计算完成,result的值为:" + result.get() + ",可以继续处理其他事情了");
}
适用于知道任务的数量,因为CountDownLatch在创建时就要指定其大小,并且不能重新初始化。
//TODO:CountDownLatch是否会禁止指令重排序?(从官方的例子看,会!有待研究)
public void example() {
CountDownLatch doneSignal = new CountDownLatch(10);
Executor e = Executors.newFixedThreadPool(10);
for (int i = 0; i < 10; ++i) // create and start threads
e.execute(new WorkerRunnable(doneSignal, i));
try {
doneSignal.await(); // wait for all to finis
} catch (InterruptedException e1) {
e1.printStackTrace();
}
}
class WorkerRunnable implements Runnable {
private final CountDownLatch doneSignal;
private final int i;
WorkerRunnable(CountDownLatch doneSignal, int i) {
this.doneSignal = doneSignal;
this.i = i;
}
public void run() {
doWork(i);
doneSignal.countDown();
}
void doWork(int i) {
}
}
其他
//TODO
作者:maxwellyue
链接:https://www.jianshu.com/p/bcbfb58d0da5
来源:简书
简书著作权归作者所有,任何形式的转载都请联系作者获得授权并注明出处。
标签:System,几种,result,doneSignal,CountDownLatch,println,多线程,等待,out 来源: https://www.cnblogs.com/xiaoshen666/p/11258556.html