RxJava Observables not Parallel - rx-java2

Question

I am new to RxJava.
I am executing a basic code :
public class App {
public static void main(String... args) throws Exception {
long startTime = System.currentTimeMillis();
abcd().map(cnt -> cnt).subscribe((s) -> System.out.println(s));
abcd().map(cnt -> cnt).subscribe(s -> System.out.println(s));
long endTime = System.currentTimeMillis();
long diff = endTime - startTime;
System.out.println(diff);
}
public static Observable<Integer> abcd() {
try {
Thread.sleep(1000);
} catch (Exception e) {
System.out.println();
}
Observable<Integer> r = Observable.fromArray(10);
return r;
}
}
Basically created two Observables & both taking 1 second in processing.
And the total time to run this code is more than 2 seconds, meaning two Observables are not executing in Parallel.
How do I change my code so as the total time of execution is 1 sec meaning two of my observable should execute in parrallel. Please post the answer wrt to RxJava.

Answer 1

You are sleeping before the Observables are even created so it's not exactly the same as Observable doing processing before it emits the result.
You can defer the execution of the abcd() method onto a background thread and wait for both to sub-flows to terminate:
Observable.merge(
Observable.defer(() -> abcd())
.subscribeOn(Schedulers.io())
.map(cnt -> cnt)
.doOnNext(System.out::println),
Observable.defer(() -> abcd())
.subscribeOn(Schedulers.io())
.map(cnt -> cnt + 1)
.doOnNext(System.out::println)
)
.blockingSubscribe(ignored -> { }, Throwable::printStackTrace);