src/main/java/io/reactivex/Flowable.java
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.UNBOUNDED_IN)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Iterable<T> blockingNext() {
        return new BlockingFlowableNext<T>(this);
    }
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.UNBOUNDED_IN)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Iterable<T> blockingNext() {
        return new BlockingFlowableNext<T>(this);
    }
Returns an {@link Iterable} that blocks until this {@code Flowable} emits another item, then
returns that item.
<p>
<img width="640" height="490" src="https://github.com/ReactiveX/RxJava/wiki/images/rx-operators/B.next.png" alt="">
<dl>
<dt><b>Backpressure:</b></dt>
<dd>The operator consumes the source {@code Flowable} in an unbounded manner
(i.e., no backpressure applied to it).</dd>
<dt><b>Scheduler:</b></dt>
<dd>{@code blockingNext} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@return an {@link Iterable} that blocks upon each iteration until this {@code Flowable} emits
a new item, whereupon the Iterable returns that item
@see <a href="http://reactivex.io/documentation/operators/takelast.html">ReactiveX documentation: TakeLast</a>