Scheduled executor

Definition

A ScheduledExecutorService runs a task after a delay or repeatedly at a fixed rate. It replaces older Timer code and keeps running other tasks even if one of them fails.

Example code

A task that runs three times, once a moment

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

class Demo {
    public static void main(String[] args) throws InterruptedException {
        ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
        AtomicInteger runs = new AtomicInteger();
        CountDownLatch threeRuns = new CountDownLatch(3);

        scheduler.scheduleAtFixedRate(() -> {
            System.out.println("tick " + runs.incrementAndGet());
            threeRuns.countDown();
        }, 0, 100, TimeUnit.MILLISECONDS);                       // start now, then every 100 ms

        threeRuns.await();
        scheduler.shutdownNow();
    }
}

// Output:
// tick 1
// tick 2
// tick 3