src/main/java/io/reactivex/Observable.java
@SuppressWarnings("unchecked")
    @CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<T> ambWith(ObservableSource<? extends T> other) {
        ObjectHelper.requireNonNull(other, "other is null");
        return ambArray(this, other);
    }
@SuppressWarnings("unchecked")
    @CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<T> ambWith(ObservableSource<? extends T> other) {
        ObjectHelper.requireNonNull(other, "other is null");
        return ambArray(this, other);
    }
Mirrors the ObservableSource (current or provided) that first either emits an item or sends a termination
notification.
<p>
<img width="640" height="385" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/ambWith.o.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code ambWith} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@param other
an ObservableSource competing to react first. A subscription to this provided source will occur after
subscribing to the current source.
@return an Observable that emits the same sequence as whichever of the source ObservableSources first
emitted an item or sent a termination notification
@see <a href="http://reactivex.io/documentation/operators/amb.html">ReactiveX operators documentation: Amb</a>