IntervalObservable.java

/*  
 * This will print values from 0 after every second.
 */
Observable.interval(1, TimeUnit.SECONDS)
                .subscribe(new Observer<Long>() {
                    @Override
                    public void onSubscribe(Disposable d) {

                    }

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

                    @Override
                    public void onError(Throwable e) {
                        System.out.println("onError: " + e.getMessage());
                    }

                    @Override
                    public void onComplete() {

                    }
                });