RxJava：虚假合并可观察调用onComplete

Question

I have several observervables I merge from a set. For some reason, the merged observable is calling onComplete, even though the individual observables are not.

Example:

Set<Observable<InputOutputEvent>> set = new HashSet<Observable<InputOutputEvent>>();
    for (Observable ob : obs) {
        ob.subscribe((e) -> {
        }, 
        (error) -> {
System.out.println("This does NOT happen.");
        }, 
        () -> {
            System.out.println("This does NOT happen.");
        });
        set.add(c.event());
    }

  Subscription s = Observable.merge(set).subscribe((e) -> {
            }, 
            (error) -> {
                System.out.println("This does NOT happen.");
            }, 
            () -> {
                System.out.println("This DOES happen.");
            });

How is that possible? Isn't the merge observable supposed to only call onComplete when all the merged ones have called it?

I've also checked for errors, but there are none.

Answer 1

Leaving this as a caution to others:

The set of observables was EMPTY. onComplete was called immediately in this case.