@Test
public void create() {

    Flowable<Integer> flowable = Flowable.fromArray(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
            .subscribeOn(Schedulers.computation());
    SubscriberBuilder<Integer, Optional<Integer>> builder = ReactiveStreams.<Integer> builder().findFirst();
    Optional<Integer> optional = ReactiveStreams.fromPublisher(flowable).filter(i -> i > 5)
            .to(builder).run().toCompletableFuture().join();
    assertThat(optional).contains(6);
}