src/main/java/io/reactivex/Flowable.java
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.ERROR)
    @SchedulerSupport(SchedulerSupport.COMPUTATION)
    public final Flowable<Flowable<T>> window(long timespan, TimeUnit unit,
            long count) {
        return window(timespan, unit, Schedulers.computation(), count, false);
    }
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.ERROR)
    @SchedulerSupport(SchedulerSupport.COMPUTATION)
    public final Flowable<Flowable<T>> window(long timespan, TimeUnit unit,
            long count) {
        return window(timespan, unit, Schedulers.computation(), count, false);
    }
Returns a Flowable that emits windows of items it collects from the source Publisher. The resulting
Publisher emits connected, non-overlapping windows, each of a fixed duration as specified by the
{@code timespan} argument or a maximum size as specified by the {@code count} argument (whichever is
reached first). When the source Publisher completes or encounters an error, the resulting Publisher
emits the current window and propagates the notification from the source Publisher.
<p>
<img width="640" height="370" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/window6.png" alt="">
<dl>
<dt><b>Backpressure:</b></dt>
<dd>The operator consumes the source {@code Publisher} in an unbounded manner.
The returned {@code Publisher} doesn't support backpressure as it uses
time to control the creation of windows. The returned inner {@code Publisher}s honor
backpressure and may hold up to {@code count} elements at most.</dd>
<dt><b>Scheduler:</b></dt>
<dd>This version of {@code window} operates by default on the {@code computation} {@link Scheduler}.</dd>
</dl>

@param timespan
the period of time each window collects items before it should be emitted and replaced with a
new window
@param unit
the unit of time that applies to the {@code timespan} argument
@param count
the maximum size of each window before it should be emitted
@return a Flowable that emits connected, non-overlapping windows of items from the source Publisher
that were emitted during a fixed duration of time or when the window has reached maximum capacity
(whichever occurs first)
@see <a href="http://reactivex.io/documentation/operators/window.html">ReactiveX operators documentation: Window</a>