Method fromOptional

src/main/java/io/reactivex/rxjava3/core/Maybe.java:6136–6142

Converts the existing value of the provided optional into a #just(Object) or an empty optional into an #empty() Maybe instance. Note that th

(@NonNull Optional<T> optional)

     * @see #empty()
     */
    @CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    @NonNull
    public static <@NonNull T> Maybe<@NonNull T> fromOptional(@NonNull Optional<T> optional) {
        Objects.requireNonNull(optional, "optional is null");
        return optional.map(Maybe::just).orElseGet(Maybe::empty);
    }

    /**
     * Signals the completion value or error of the given (hot) {@link CompletionStage}-based asynchronous calculation.