limit123.java

  @Test
  public void observableLimit2() throws Exception {
    long lowerBound = 0;
    long higherBound = 1000;

    long actualSum = (higherBound * (higherBound + 1)) / 2;

    Single<Long> longSingle = Flowable.rangeLong(lowerBound, higherBound + 1)
        .doOnNext(aLong -> System.out.println(Thread.currentThread().toString()))
        .reduce(0L, (integer, aLong) -> {
          return integer + aLong;
        })
        .subscribeOn(Schedulers.io()); // do not do this for accumulating 1000 numbers. Switching between Thread / Tasks is expensive

    longSingle.test().await().assertResult(actualSum);
  }