@Test
    public void testSkipLastObservable() throws InterruptedException {

        Observable.just("A", "B", "C", "D", "E", "F", "G", "H", "I", "J")
                .skipLast(4)
                .subscribe(new Observer<String>() {
                    @Override
                    public void onSubscribe(Disposable d) {

                    }

                    @Override
                    public void onNext(String s) {
                        System.out.println("onNext: " + s);
                    }

                    @Override
                    public void onError(Throwable e) {

                    }

                    @Override
                    public void onComplete() {

                    }
                });
    }