rx java parallel demo

Rx.java

public class Rx {
    public static void main(String[] args) {
        int threadNum = Runtime.getRuntime().availableProcessors() + 1;
        ExecutorService executor = Executors.newFixedThreadPool(threadNum);
        final Scheduler scheduler = Schedulers.from(executor);
        Observable.range(1, 20)
                .flatMap(x -> {
                    Observable<Integer> observableA = Observable.just(x).observeOn(scheduler).map(a -> {
                        System.out.println(Thread.currentThread().getName() + ": =observableA=> " + a);
                        return a;
                    });
                    Observable<Integer> observableB = Observable.just(x).observeOn(scheduler).map(b -> {
                        System.out.println(Thread.currentThread().getName() + ": =observableB=> " + b);
                        return b;
                    });
                    return Observable.combineLatest(observableA, observableB, (a, b) -> {
                        System.out.println(Thread.currentThread().getName() + ": =combineLatest=> " + "a = " + a + ", b = " + b);
                        return a + b;
                    }).subscribeOn(scheduler).map(y -> {
                        System.out.println(Thread.currentThread().getName() + ": =scheduler=> " + y);
                        return y;
                    });
                }).subscribe(x -> {
                    System.out.println(Thread.currentThread().getName() + ": =main=> " + x);
                }, Throwable::printStackTrace, executor::shutdown);
    }
}