src/main/java/io/reactivex/Flowable.java
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Flowable<Flowable<T>> window(long count, long skip, int bufferSize) {
        ObjectHelper.verifyPositive(skip, "skip");
        ObjectHelper.verifyPositive(count, "count");
        ObjectHelper.verifyPositive(bufferSize, "bufferSize");
        return RxJavaPlugins.onAssembly(new FlowableWindow<T>(this, count, skip, bufferSize));
    }
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Flowable<Flowable<T>> window(long count, long skip, int bufferSize) {
        ObjectHelper.verifyPositive(skip, "skip");
        ObjectHelper.verifyPositive(count, "count");
        ObjectHelper.verifyPositive(bufferSize, "bufferSize");
        return RxJavaPlugins.onAssembly(new FlowableWindow<T>(this, count, skip, bufferSize));
    }
Returns a Flowable that emits windows of items it collects from the source Publisher. The resulting
Publisher emits windows every {@code skip} items, each containing no more than {@code count} items. 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="365" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/window4.png" alt="">
<dl>
<dt><b>Backpressure:</b></dt>
<dd>The operator honors backpressure of its inner and outer subscribers, however, the inner Publisher uses an
unbounded buffer that may hold at most {@code count} elements.</dd>
<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
@param skip
how many items need to be skipped before starting a new window. Note that if {@code skip} and
{@code count} are equal this is the same operation as {@link #window(long)}.
@param bufferSize
the capacity hint for the buffer in the inner windows
@return a Flowable that emits windows every {@code skip} items containing at most {@code count} items
from the source Publisher
@throws IllegalArgumentException if either count or skip is non-positive
@see <a href="http://reactivex.io/documentation/operators/window.html">ReactiveX operators documentation: Window</a>