src/main/java/io/reactivex/Maybe.java
@CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public static <T> Maybe<T> just(T item) {
        ObjectHelper.requireNonNull(item, "item is null");
        return RxJavaPlugins.onAssembly(new MaybeJust<T>(item));
    }
@CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public static <T> Maybe<T> just(T item) {
        ObjectHelper.requireNonNull(item, "item is null");
        return RxJavaPlugins.onAssembly(new MaybeJust<T>(item));
    }
Returns a {@code Maybe} that emits a specified item.
<p>
<img width="640" height="485" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Maybe.just.png" alt="">
<p>
To convert any object into a {@code Maybe} that emits that object, pass that object into the
{@code just} method.
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code just} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@param item
the item to emit
@param <T>
the type of that item
@return a {@code Maybe} that emits {@code item}
@see <a href="http://reactivex.io/documentation/operators/just.html">ReactiveX operators documentation: Just</a>