PeekStageFactory implements ProcessingStageFactory<Stage.Peek> { @SuppressWarnings("unchecked") @Override public <I, O> ProcessingStage<I, O> create(Engine engine, Stage.Peek stage) { Consumer<I> consumer = (Consumer<I>) Objects.requireNonNull(stage) .getConsumer(); Objects.requireNonNull(consumer); return source -> (Flowable<O>) source.doOnNext(consumer::accept); }  @SuppressWarnings("unchecked") @Override ProcessingStage<I, O> create(Engine engine, Stage.Peek stage);  }
@Test public void create() throws ExecutionException, InterruptedException { Flowable<Integer> flowable = Flowable.fromArray(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) .subscribeOn(Schedulers.computation()); List<Integer> squares = new ArrayList<>(); List<String> strings = new ArrayList<>(); List<String> list = ReactiveStreams.fromPublisher(flowable) .filter(i -> i < 4) .map(this::square) .peek(squares::add) .map(this::asString) .peek(strings::add) .toList() .run().toCompletableFuture().get(); assertThat(list).containsExactly("1", "4", "9"); assertThat(squares).containsExactly(1, 4, 9); assertThat(strings).containsExactly("1", "4", "9"); }
@Test(expected = NullPointerException.class) public void createWithoutStage() { factory.create(null, null); }
@Test(expected = NullPointerException.class) public void createWithoutFunction() { factory.create(null, () -> null); }