src/main/java/io/reactivex/Maybe.java
@CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public final <R> Maybe<R> concatMap(Function<? super T, ? extends MaybeSource<? extends R>> mapper) {
        ObjectHelper.requireNonNull(mapper, "mapper is null");
        return RxJavaPlugins.onAssembly(new MaybeFlatten<T, R>(this, mapper));
    }
@CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public final <R> Maybe<R> concatMap(Function<? super T, ? extends MaybeSource<? extends R>> mapper) {
        ObjectHelper.requireNonNull(mapper, "mapper is null");
        return RxJavaPlugins.onAssembly(new MaybeFlatten<T, R>(this, mapper));
    }
@ CheckReturnValue @ NonNull @ SchedulerSupport ( SchedulerSupport . NONE ) public final < R > Maybe < R > concatMap ( Function < ? super T , ? extends MaybeSource < ? extends R > > mapper ) { ObjectHelper . requireNonNull ( mapper , "mapper is null" ) ; return RxJavaPlugins . onAssembly ( new MaybeFlatten < T , R > ( this , mapper ) ) ; }
Returns a Maybe that is based on applying a specified function to the item emitted by the source Maybe,
where that function returns a MaybeSource.
<p>
<img width="640" height="356" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Maybe.flatMap.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code concatMap} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>
<p>Note that flatMap and concatMap for Maybe is the same operation.
@param <R> the result value type
@param mapper
a function that, when applied to the item emitted by the source Maybe, returns a MaybeSource
@return the Maybe returned from {@code func} when applied to the item emitted by the source Maybe
@see <a href="http://reactivex.io/documentation/operators/flatmap.html">ReactiveX operators documentation: FlatMap</a>
Returns a Maybe that is based on applying a specified function to the item emitted by the source Maybe where that function returns a MaybeSource . <p > <img width = 640 height = 356 src = https : // raw . github . com / wiki / ReactiveX / RxJava / images / rx - operators / Maybe . flatMap . png alt = > <dl > <dt > <b > Scheduler : < / b > < / dt > <dd > {