src/main/java/io/reactivex/Observable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<T> switchIfEmpty(ObservableSource<? extends T> other) {
        ObjectHelper.requireNonNull(other, "other is null");
        return RxJavaPlugins.onAssembly(new ObservableSwitchIfEmpty<T>(this, other));
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<T> switchIfEmpty(ObservableSource<? extends T> other) {
        ObjectHelper.requireNonNull(other, "other is null");
        return RxJavaPlugins.onAssembly(new ObservableSwitchIfEmpty<T>(this, other));
    }
@ CheckReturnValue @ SchedulerSupport ( SchedulerSupport . NONE ) public final Observable < T > switchIfEmpty ( ObservableSource < ? extends T > other ) { ObjectHelper . requireNonNull ( other , "other is null" ) ; return RxJavaPlugins . onAssembly ( new ObservableSwitchIfEmpty < T > ( this , other ) ) ; }
Returns an Observable that emits the items emitted by the source ObservableSource or the items of an alternate
ObservableSource if the source ObservableSource is empty.
<p>
<img width="640" height="255" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/switchifempty.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 ObservableSource to subscribe to if the source does not emit any items
@return  an ObservableSource that emits the items emitted by the source ObservableSource or the items of an
alternate ObservableSource if the source ObservableSource is empty.
@since 1.1.0
Returns an Observable that emits the items emitted by the source ObservableSource or the items of an alternate ObservableSource if the source ObservableSource is empty . <p > <img width = 640 height = 255 src = https : // raw . github . com / wiki / ReactiveX / RxJava / images / rx - operators / switchifempty . png alt = > <dl > <dt > <b > Scheduler : < / b > < / dt > <dd > { @code switchIfEmpty } does not operate by default on a particular { @link Scheduler } . < / dd > < / dl >