src/main/java/io/reactivex/Flowable.java
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.COMPUTATION)
    public final <R> Flowable<R> replay(Function<? super Flowable<T>, ? extends Publisher<R>> selector, int bufferSize, long time, TimeUnit unit) {
        return replay(selector, bufferSize, time, unit, Schedulers.computation());
    }
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.COMPUTATION)
    public final <R> Flowable<R> replay(Function<? super Flowable<T>, ? extends Publisher<R>> selector, int bufferSize, long time, TimeUnit unit) {
        return replay(selector, bufferSize, time, unit, Schedulers.computation());
    }
Returns a Flowable that emits items that are the results of invoking a specified selector on items
emitted by a {@link ConnectableFlowable} that shares a single subscription to the source Publisher,
replaying no more than {@code bufferSize} items that were emitted within a specified time window.
<p>
Note that due to concurrency requirements, {@code replay(bufferSize)} may hold strong references to more than
{@code bufferSize} source emissions.
<p>
<img width="640" height="445" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/replay.fnt.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} operates by default on the {@code computation} {@link Scheduler}.</dd>
</dl>

@param <R>
the type of items emitted by the resulting Publisher
@param selector
a selector function, which can use the multicasted sequence as many times as needed, without
causing multiple subscriptions to the Publisher
@param bufferSize
the buffer size that limits the number of items the connectable Publisher can replay
@param time
the duration of the window in which the replayed items must have been emitted
@param unit
the time unit of {@code time}
@return a Flowable that emits items that are the results of invoking the selector on items emitted by
a {@link ConnectableFlowable} that shares a single subscription to the source Publisher, and
replays no more than {@code bufferSize} items that were emitted within the window defined by
{@code time}
@see <a href="http://reactivex.io/documentation/operators/replay.html">ReactiveX operators documentation: Replay</a>