Observable.just(1,2,3,4,5)
        .ignoreElements()
        .subscribe(new CompletableObserver() {
            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, "onSubscribe");
            }
            @Override
            public void onComplete() {
                Log.d(TAG, "onComplete");
            }
            @Override
            public void onError(Throwable e) {
                Log.d(TAG, "onError");
            }
        });