Pagination with backpressure

Pager.java

import rx.Observable;

public class Pager {

    public static void main(String[] args) {
        Observable.range(1, 1000)
                  .window(10)
                  .doOnNext(nextBatch -> System.out.println("Next page."))
                  .flatMap(nums -> nums, 1)
                  .forEach(System.out::println);
    }
}

What your code is doing is fetching 1000 JSON elements over the network, then traversing them in batches of 10. Not very efficient!

Actually not, if the source supports backpressure. If you were to replace Observable.range(1, 1000) with a real HTTP request over the wire, you would make calls for a page per request(n) from the subscriber. So, you would just be querying one page at a time from the server.

Another thing to keep in mind, how would you retry the last page in your example?

I think what is more interesting in what you are asking is how does someone navigate between pages, eg: prev, next, jump to page # usecases. Since, RxJava backpressure always "moves forward", there is no way to address that solely by using backpressure.