src/main/java/io/reactivex/Maybe.java
@CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Maybe<T> switchIfEmpty(MaybeSource<? extends T> other) {
        ObjectHelper.requireNonNull(other, "other is null");
        return RxJavaPlugins.onAssembly(new MaybeSwitchIfEmpty<T>(this, other));
    }
@CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Maybe<T> switchIfEmpty(MaybeSource<? extends T> other) {
        ObjectHelper.requireNonNull(other, "other is null");
        return RxJavaPlugins.onAssembly(new MaybeSwitchIfEmpty<T>(this, other));
    }
Returns a Maybe that emits the items emitted by the source Maybe or the items of an alternate
MaybeSource if the current Maybe is empty.
<p>
<img width="640" height="445" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/switchifempty.m.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code switchIfEmpty} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@param other
the alternate MaybeSource to subscribe to if the main does not emit any items
@return  a Maybe that emits the items emitted by the source Maybe or the items of an
alternate MaybeSource if the source Maybe is empty.