Learning RxJava

Observable.never()

A close cousin of Observable.empty() is Observable.never(). The only difference between them is that it never calls onComplete(), forever leaving observers waiting for emissions but never actually giving any:

    import io.reactivex.Observable;    public class Launcher {      public static void main(String[] args) {        Observable<String> empty = Observable.never();        empty.subscribe(System.out::println,          Throwable::printStackTrace,            () -> System.out.println("Done!"));        sleep(5000);      }      public static void sleep(int millis) {        try {          Thread.sleep(millis);        } catch (InterruptedException e) {          e.printStackTrace();        }       }     } 

This Observable is primarily used for testing and not that often in production. We have to use sleep() here just like Observable.interval() ...