在Java中的另一个任务中创建任务

Question

我编写了一个将任务提交给 ExecutorService 的函数。该函数有一个条件，如果为真，函数将调用自身来创建另一个任务。

private void taskCreator(int v, ExecutorService executor) {
    executor.submit(() -> {
        if (// some condition) {
            taskCreator(u, executor);
        }
    });
}

如何才能等到所有任务完成？

我尝试将Future与方法get()一起使用，但主线程在ExecutorService之前完成执行。我也不知道会有多少任务。

Answer 1

比如这样

public class ExecutorServiceDemo {

    public static void main(String[] args) throws InterruptedException, ExecutionException {
        ExecutorService service = Executors.newFixedThreadPool(10);
        try {
            List<Future<?>> futures = new ArrayList<>();
            for (int index = 0; index < 100; index++) {
                final int number = index;
                futures.add(service.submit(() -> {
                    try {
                        System.out.println("Task " + number + " startup");
                        Thread.sleep(1000);
                        System.out.println("Task " + number + " shutdown");

                    } catch (InterruptedException exception) {
                        Thread.currentThread().interrupt();
                    }
                }));
            }
            // Wait for all threads to finish
            for (Future<?> future : futures) {
                future.get();
            }
        } finally {
            service.shutdown();
            if (!service.awaitTermination(10, java.util.concurrent.TimeUnit.SECONDS))  {
                service.shutdownNow();
            }
        }
    }
}