Method just

src/main/java/io/reactivex/rxjava3/core/Flowable.java:3032–3039

Returns a Flowable that signals the given (constant reference) item and then completes. Note that the item is taken and re-emitted as is and not computed by any me

(T item)

     * @see #fromIterable(Iterable)
     */
    @CheckReturnValue
    @NonNull
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public static <@NonNull T> Flowable<T> just(T item) {
        Objects.requireNonNull(item, "item is null");
        return RxJavaPlugins.onAssembly(new FlowableJust<>(item));
    }

    /**
     * Converts two items into a {@link Publisher} that emits those items.