Optional fromNullable()

[Michael Hixson]

First, I'll venture to say that debates about Optional took up way
more time than they were worth, and your reasonable suggestion may be
met with silence.  But I had the same reaction initially, so I'll join
in.

This has extremely low utility because it can be done with a trivial
method in your own code:

  public static <T> Optional<T> fromNullable(T object) {
    return (object == null) ? Optional.empty() : Optional.of(object);
  }

Your implementation will be just as good as the JDK's theoretical
implementation.  There are no tricks.  It's simple.  Write it once,
it's good forever.

That said, I don't understand why Optional.of doesn't have this
behavior itself.  That is, I don't understand why Optional.of(null)
throws instead of returning Optional.empty().  The current
implementation stands in a weird middle ground of hand-holdiness:  it
doesn't want to provide you with the obvious solution of converting
nullable references to Optionals because you should do that yourself,
it doesn't want you to toss around nulls carelessly so it throws NPE
on Optional.of(null), even though it suspiciously accepts null
arguments to orElse, and it doesn't trust that users who think about
null would do Optional.of(Objects.requireNonNull(object)).  There's a
peculiar, focused behavior there.  The JDK is on safe ground offering
Optional.of with Guava's behavior because it's been battle-tested, but
it sure is confusing to me.

-Michael

On Fri, Apr 26, 2013 at 12:30 AM, Seibt, Volker
<volker.seibt at buenting.de> wrote:
> In contrast to the Guava API Optional class in Java contains no static method "fromNullable()" which allows null-values and  analogous should deliver Optional.empty() in this case.
>
> It seems to be very comfortable in later "Optionalizing" return values like e.g.
>
> Optional<T> o = Optional.fromNullable(map.get(key));
>
> instead of
>
> Optional<T> o = map.get(key) == null ? Optional.empty() :  Optional.of(map(key));
>
> or worse readable
>
> T t = map.get(key);
> Optional<T> o = t == null ? Optional.empty() :  Optional.of(t);
>
> to avoid calling map(..) twice.
>
>
> Is there a reason why it's omitted?
>
>