AmbObservable.java

        Observable<Integer> observable1 = Observable.timer(4, TimeUnit.SECONDS)
                .flatMap(new Function<Long, ObservableSource<Integer>>() {
                    @Override
                    public ObservableSource<Integer> apply(Long aLong) throws Exception {
                        return Observable.just(10, 20, 30, 40, 50);
                    }
                });

        Observable<Integer> observable2 = Observable.timer(3, TimeUnit.SECONDS)
                .flatMap(new Function<Long, ObservableSource<Integer>>() {
                    @Override
                    public ObservableSource<Integer> apply(Long aLong) throws Exception {
                        return Observable.just(100, 200, 300, 400, 500);
                    }
                });

        Observable
                .ambArray(observable1, 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() {

                    }
                });

        Thread.sleep(5000);