src/main/java/io/reactivex/Maybe.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Single<Long> count() {
        return RxJavaPlugins.onAssembly(new MaybeCount<T>(this));
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Single<Long> count() {
        return RxJavaPlugins.onAssembly(new MaybeCount<T>(this));
    }
Returns a Maybe that counts the total number of items emitted (0 or 1) by the source Maybe and emits
this count as a 64-bit Long.
<p>
<img width="640" height="310" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/longCount.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code count} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@return a Single that emits a single item: the number of items emitted by the source Maybe as a
64-bit Long item
@see <a href="http://reactivex.io/documentation/operators/count.html">ReactiveX operators documentation: Count</a>
@see #count()