src/main/java/io/reactivex/Observable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.CUSTOM)
    public final Observable<Observable<T>> window(long timespan, long timeskip, TimeUnit unit, Scheduler scheduler, int bufferSize) {
        ObjectHelper.verifyPositive(timespan, "timespan");
        ObjectHelper.verifyPositive(timeskip, "timeskip");
        ObjectHelper.verifyPositive(bufferSize, "bufferSize");
        ObjectHelper.requireNonNull(scheduler, "scheduler is null");
        ObjectHelper.requireNonNull(unit, "unit is null");
        return RxJavaPlugins.onAssembly(new ObservableWindowTimed<T>(this, timespan, timeskip, unit, scheduler, Long.MAX_VALUE, bufferSize, false));
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.CUSTOM)
    public final Observable<Observable<T>> window(long timespan, long timeskip, TimeUnit unit, Scheduler scheduler, int bufferSize) {
        ObjectHelper.verifyPositive(timespan, "timespan");
        ObjectHelper.verifyPositive(timeskip, "timeskip");
        ObjectHelper.verifyPositive(bufferSize, "bufferSize");
        ObjectHelper.requireNonNull(scheduler, "scheduler is null");
        ObjectHelper.requireNonNull(unit, "unit is null");
        return RxJavaPlugins.onAssembly(new ObservableWindowTimed<T>(this, timespan, timeskip, unit, scheduler, Long.MAX_VALUE, bufferSize, false));
    }
Returns an Observable that emits windows of items it collects from the source ObservableSource. The resulting
ObservableSource starts a new window periodically, as determined by the {@code timeskip} argument. It emits
each window after a fixed timespan, specified by the {@code timespan} argument. When the source
ObservableSource completes or 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="335" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/window7.s.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>You specify which {@link Scheduler} this operator will use.</dd>
</dl>

@param timespan
the period of time each window collects items before it should be emitted
@param timeskip
the period of time after which a new window will be created
@param unit
the unit of time that applies to the {@code timespan} and {@code timeskip} arguments
@param scheduler
the {@link Scheduler} to use when determining the end and start of a window
@param bufferSize
the capacity hint for the buffer in the inner windows
@return an Observable that emits new windows periodically as a fixed timespan elapses
@see <a href="http://reactivex.io/documentation/operators/window.html">ReactiveX operators documentation: Window</a>