TakeUntilObservable.java

        Observable<Integer> observable1 = Observable
                .create(emitter -> {
                    for(int i=0; i<= 6; i++) {
                        Thread.sleep(1000);
                        emitter.onNext(i);
                    }
                    emitter.onComplete();
                });

        Observable<Integer> observable2 = Observable
                .timer(3, TimeUnit.SECONDS)
                .flatMap(__ -> Observable.just(11, 12, 13, 14, 15, 16));

        observable1.takeUntil(observable2)
                .subscribe(new Observer<Integer>() {
                    @Override
                    public void onSubscribe(Disposable d) {

                    }

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

                    @Override
                    public void onError(Throwable e) {

                    }

                    @Override
                    public void onComplete() {

                    }
                });