Learning RxJava - Second Edition

Observable.empty()

Although this may not seem useful yet, it is sometimes helpful to create an Observable that emits nothing and calls onComplete():

import io.reactivex.rxjava3.core.Observable;public class Ch2_20 {    public static void main(String[] args) {        Observable<String> empty = Observable.empty();        empty.subscribe(System.out::println,                Throwable::printStackTrace,                () -> System.out.println("Done!"));    }}

The output is as follows:

Done!

Note that no emissions were printed because there were none. It went straight to emitting the onComplete event processed by the third parameter of the subscribe(Consumer<String> onNext, Consumer<Throwable> onError, Action onComplete) method, which printed the Done! message.

Empty observables typically represent ...