我需要一次执行一定数量的任务4，就像这样:
ExecutorService taskExecutor = Executors.newFixedThreadPool(4);
while(...) {
taskExecutor.execute(new MyTask());
}
//...wait for completion somehow
当所有这些都完成后，我如何得到通知?现在我想不出比设置一些全局任务计数器更好的方法，并在每个任务结束时减少它，然后在无限循环中监视这个计数器变成0;或获取一个期货列表，并在无限循环监视器isDone为所有它们。不涉及无限循环的更好的解决方案是什么?
谢谢。
当前回答
基本上在ExecutorService上调用shutdown()，然后调用awaitterminate ():
ExecutorService taskExecutor = Executors.newFixedThreadPool(4);
while(...) {
taskExecutor.execute(new MyTask());
}
taskExecutor.shutdown();
try {
taskExecutor.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
} catch (InterruptedException e) {
...
}
其他回答
ExecutorService WORKER_THREAD_POOL
= Executors.newFixedThreadPool(10);
CountDownLatch latch = new CountDownLatch(2);
for (int i = 0; i < 2; i++) {
WORKER_THREAD_POOL.submit(() -> {
try {
// doSomething();
latch.countDown();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
});
}
// wait for the latch to be decremented by the two remaining threads
latch.await();
如果doSomething()抛出一些其他异常，latch.countDown()似乎不会执行，那么我该怎么办?
在Java8中，你可以用CompletableFuture来实现:
ExecutorService es = Executors.newFixedThreadPool(4);
List<Runnable> tasks = getTasks();
CompletableFuture<?>[] futures = tasks.stream()
.map(task -> CompletableFuture.runAsync(task, es))
.toArray(CompletableFuture[]::new);
CompletableFuture.allOf(futures).join();
es.shutdown();
基本上在ExecutorService上调用shutdown()，然后调用awaitterminate ():
ExecutorService taskExecutor = Executors.newFixedThreadPool(4);
while(...) {
taskExecutor.execute(new MyTask());
}
taskExecutor.shutdown();
try {
taskExecutor.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
} catch (InterruptedException e) {
...
}
你可以在这个Runner类上调用waitTillDone():
Runner runner = Runner.runner(4); // create pool with 4 threads in thread pool
while(...) {
runner.run(new MyTask()); // here you submit your task
}
runner.waitTillDone(); // and this blocks until all tasks are finished (or failed)
runner.shutdown(); // once you done you can shutdown the runner
在调用shutdown()之前，您可以重用这个类并多次调用waitTillDone()，而且您的代码非常简单。你也不需要预先知道任务的数量。
要使用它，只需将gradle/maven compile 'com.github.matejtymes:javafixes:1.3.1'依赖项添加到你的项目中。
详情请点击这里:
https://github.com/MatejTymes/JavaFixes
这只是我的个人意见。 为了克服CountDownLatch预先知道任务数量的要求，您可以使用简单的Semaphore来使用旧的方式。
ExecutorService taskExecutor = Executors.newFixedThreadPool(4);
int numberOfTasks=0;
Semaphore s=new Semaphore(0);
while(...) {
taskExecutor.execute(new MyTask());
numberOfTasks++;
}
try {
s.aquire(numberOfTasks);
...
在任务中调用s.release()就像调用latch.countDown()一样;
