PublishSubjectMergeUsage.java

class PublishSubjectMergeUsage {

    PublishSubject<List<Car>> cars = PublishSubject.create(...); //Car has some Id

    PublishSubject<List<Wheel>> wheels = PublishSubject.create(...); //Wheel have carId which is


    public Observable<List<CarWithWheels>> test(Observable<List<Car>> cars, Observable<List<Wheel>> wheels) {
        return Observable.combineLatest(
                cars.flatMapIterable(c -> c),
                wheels.flatMapIterable(w -> w).toMap(Wheel::carId),
                (car, wheelsMap) -> new CarWithWheels(car, wheelsMap.get(car.id))
        ).toList();
    }

    public subscriptionShouldFireEveryTimeCarsOrWheelsPublishesNewList() {
        test(cars, wheels).subscribe(...);
    }
}