src/main/java/io/reactivex/Flowable.java
@BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final void blockingSubscribe(Consumer<? super T> onNext, Consumer<? super Throwable> onError, Action onComplete,
        int bufferSize) {
        FlowableBlockingSubscribe.subscribe(this, onNext, onError, onComplete, bufferSize);
    }
@BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final void blockingSubscribe(Consumer<? super T> onNext, Consumer<? super Throwable> onError, Action onComplete,
        int bufferSize) {
        FlowableBlockingSubscribe.subscribe(this, onNext, onError, onComplete, bufferSize);
    }
Subscribes to the source and calls the given callbacks <strong>on the current thread</strong>.
<p>
Note that calling this method will block the caller thread until the upstream terminates
normally or with an error. Therefore, calling this method from special threads such as the
Android Main Thread or the Swing Event Dispatch Thread is not recommended.
<dl>
<dt><b>Backpressure:</b></dt>
<dd>The operator consumes the source {@code Flowable} in an bounded manner (up to bufferSize
outstanding request amount for items).</dd>
<dt><b>Scheduler:</b></dt>
<dd>{@code blockingSubscribe} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>
<p>History: 2.1.15 - experimental
@param onNext the callback action for each source value
@param onError the callback action for an error event
@param onComplete the callback action for the completion event.
@param bufferSize the size of the buffer
@since 2.2