src/main/java/io/reactivex/Observable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final <B> Observable<Observable<T>> window(ObservableSource<B> boundary) {
        return window(boundary, bufferSize());
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final <B> Observable<Observable<T>> window(ObservableSource<B> boundary) {
        return window(boundary, bufferSize());
    }
@ CheckReturnValue @ SchedulerSupport ( SchedulerSupport . NONE ) public final < B > Observable < Observable < T > > window ( ObservableSource < B > boundary ) { return window ( boundary , bufferSize ( ) ) ; }
Returns an Observable that emits non-overlapping windows of items it collects from the source ObservableSource
where the boundary of each window is determined by the items emitted from a specified boundary-governing
ObservableSource.
<p>
<img width="640" height="475" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/window8.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 <B>
the window element type (ignored)
@param boundary
an ObservableSource whose emitted items close and open windows
@return an Observable that emits non-overlapping windows of items it collects from the source ObservableSource
where the boundary of each window is determined by the items emitted from the {@code boundary}
ObservableSource
@see <a href="http://reactivex.io/documentation/operators/window.html">ReactiveX operators documentation: Window</a>
Returns an Observable that emits non - overlapping windows of items it collects from the source ObservableSource where the boundary of each window is determined by the items emitted from a specified boundary - governing ObservableSource . <p > <img width = 640 height = 475 src = https : // raw . github . com / wiki / ReactiveX / RxJava / images / rx - operators / window8 . 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 >