RxJava recursion (in response to https://medium.com/@stevenlow1983/rx-java-and-recursion-719f8ee1977a)

ObservableTest.java

public class ObservableTest {

    @Test
    public void observable_withRecursion_returnsAllObjects() {
        final int maxPageNum = 15;
        getIntegers(1, 5, maxPageNum)
                .subscribe(System.out::println);
    }

    private Observable<Integer> getIntegers(final int pageStart, final int pageSize, final int maxPageNum) {
        return Observable.just(pageStart)
                .filter(page -> page < maxPageNum)
                .flatMap(page -> Observable.range(page, pageSize)
                        .concatWith(getIntegers(pageStart + pageSize, pageSize, maxPageNum)));
    }
}