src/main/java/io/reactivex/Observable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<Observable<T>> window(long count) {
        return window(count, count, bufferSize());
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<Observable<T>> window(long count) {
        return window(count, count, bufferSize());
    }
Returns an Observable that emits windows of items it collects from the source ObservableSource. The resulting
ObservableSource emits connected, non-overlapping windows, each containing {@code count} items. When the source
ObservableSource completes or encounters an error, the resulting ObservableSource emits the current window and
propagates the notification from the source ObservableSource.
<p>
<img width="640" height="400" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/window3.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>This version of {@code window} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@param count
the maximum size of each window before it should be emitted
@return an Observable that emits connected, non-overlapping windows, each containing at most
{@code count} items from the source ObservableSource
@throws IllegalArgumentException if either count is non-positive
@see <a href="http://reactivex.io/documentation/operators/window.html">ReactiveX operators documentation: Window</a>