src/main/java/io/reactivex/Flowable.java
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final ConnectableFlowable<T> replay() {
        return FlowableReplay.createFrom(this);
    }
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final ConnectableFlowable<T> replay() {
        return FlowableReplay.createFrom(this);
    }
Returns a {@link ConnectableFlowable} that shares a single subscription to the underlying Publisher
that will replay all of its items and notifications to any future {@link Subscriber}. A Connectable
Publisher resembles an ordinary Publisher, except that it does not begin emitting items when it is
subscribed to, but only when its {@code connect} method is called.
<p>
<img width="640" height="515" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/replay.png" alt="">
<dl>
<dt><b>Backpressure:</b></dt>
<dd>This operator supports backpressure. Note that the upstream requests are determined by the child
Subscriber which requests the largest amount: i.e., two child Subscribers with requests of 10 and 100 will
request 100 elements from the underlying Publisher sequence.</dd>
<dt><b>Scheduler:</b></dt>
<dd>This version of {@code replay} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@return a {@link ConnectableFlowable} that upon connection causes the source Publisher to emit its
items to its {@link Subscriber}s
@see <a href="http://reactivex.io/documentation/operators/replay.html">ReactiveX operators documentation: Replay</a>