src/main/java/io/reactivex/Flowable.java
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.UNBOUNDED_IN)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Disposable subscribe(Consumer<? super T> onNext) {
        return subscribe(onNext, Functions.ON_ERROR_MISSING,
                Functions.EMPTY_ACTION, FlowableInternalHelper.RequestMax.INSTANCE);
    }
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.UNBOUNDED_IN)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Disposable subscribe(Consumer<? super T> onNext) {
        return subscribe(onNext, Functions.ON_ERROR_MISSING,
                Functions.EMPTY_ACTION, FlowableInternalHelper.RequestMax.INSTANCE);
    }
Subscribes to a Publisher and provides a callback to handle the items it emits.
<p>
If the Flowable emits an error, it is wrapped into an
{@link io.reactivex.exceptions.OnErrorNotImplementedException OnErrorNotImplementedException}
and routed to the RxJavaPlugins.onError handler.
<dl>
<dt><b>Backpressure:</b></dt>
<dd>The operator consumes the source {@code Publisher} in an unbounded manner (i.e., no
backpressure is applied to it).</dd>
<dt><b>Scheduler:</b></dt>
<dd>{@code subscribe} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@param onNext
the {@code Consumer<T>} you have designed to accept emissions from the Publisher
@return a {@link Disposable} reference with which the caller can stop receiving items before
the Publisher has finished sending them
@throws NullPointerException
if {@code onNext} is null
@see <a href="http://reactivex.io/documentation/operators/subscribe.html">ReactiveX operators documentation: Subscribe</a>