add Optional.stream()

[hoeggi]

Let's you convert an Optional to a Stream. Useful if you have a @Nullable list.

Instead of this

    private static <T> Stream<T> stream(@Nullable T object) {
        return Optional.of(object).map(value -> {
            if (value instanceof Iterable) {
                return Stream.stream((Iterable<T>) value);
            } else {
                return Stream.of(value);
            }
        }).or(Stream.of());
    }

you get this

    private static <T> Stream<T> stream(@Nullable T object) {
        return Optional.of(object).stream();
    }

[artemohanjanyan]

Looks a bit confusing, single method with different logic for different types. I'd prefer writing optional.stream().flatten() explicitly.
Also, no tests.

[hoeggi]

Ok, thx for the feedback. Just to define what flatten does.
If you call flatten on a Stream<Iterable<T>> you get a Stream<T>
where a Stream<Value> from something like Stream.of(T value) keeps the same structure?

[artemohanjanyan]

It's .flatMap(x -> x) :)