Why interval doesn't emit anything?

Question

Why this code doesn't emit anything:

Observable<Long> observable1 = Observable.interval(3, 1000, TimeUnit.MILLISECONDS);
observable1.subscribe(l -> System.out.println(l));

Answer 1

intervall() operates on Scheduler.computation(), which allocates a new thread. Your program terminates before the new thread has a chance to run. You can solve that by suspending the main thread for a while.

Observable<Long> observable1 = Observable.interval(3, 1000, TimeUnit.MILLISECONDS);
observable1.subscribe(l -> System.out.println(l));

try {
    Thread.sleep(5000);
}
catch(InterruptedException e) { }

Now, you will see some output.