如何验证ScheduledExecutorService已启动？

Question

Description

A task A is running, that can last from 2s to 60+s.

While A is running, I scheduled a ExecutorService that after 10s (delay), would print "running" every 5s (fixed rate).

ScheduledExecutorService scheduleNotifications = Executors
        .newSingleThreadScheduledExecutor();
scheduleNotifications.scheduleAtFixedRate(new Runnable() {
    @Override
    public void run() {
        System.out.println("A is running");
    }
}, 10, 5, TimeUnit.SECONDS);

Once A is done, I wish to print "A is done." but only if my ScheduledExecutorService task has started , meaning it printed "running" at least once.

• If A finished before 10s, I do not print anything.
• If A takes more than 10s, I print "running" every 5s and then "done" once A is finished.

How could I do that without using a boolean flag inside the schduled runnable . Is there a way to check that my service started?

Answer 1

ScheduledThreadPoolExecutor scheduler = new ScheduledThreadPoolExecutor(1);
scheduler.scheduleAtFixedRate(new Runnable() {
    @Override
    public void run() {
        System.out.println("A is running");
    }
}, 10, 5, TimeUnit.SECONDS);

Thread.sleep(20000);
scheduler.shutdown();
if (scheduler.getCompletedTaskCount() > 0) {
    System.out.println("A is done.");
}