SwitchOnNextObservable.java

        Observable
                /* This is the outer observable. Items emitted here will be used to control the inner observable. 
                 * Whenever it emits an item, the inner observable will stop its emission 
                 * and a new one will be created.
                 */
                .switchOnNext(Observable.interval(600, TimeUnit.MILLISECONDS)

            .map((aLong) -> {
            /* This is the inner observable. It will emit items every 180ms. 
             * When the outer observable emits a new item (which is supposed to happen after 600ms) 
             * this one will be discarded and a new one will be taken in place.
             * Since outer observable will emit items each 600ms, inner observable will have a chance to emit 3 items and
             * then be discarded. */
                return Observable.interval(180, TimeUnit.MILLISECONDS);
            }))

            .subscribe(item -> System.out.println("onNext: " + item));

        Thread.sleep(5000);