RFR(s): 8140281 add no-arg Optional.orElseThrow() as preferred alternative to get()

[Remi Forax]

Let's gently derail this thread, the is another pain point with the current optional API,
it seems that are no simple way to transform an Optional<Integer> to an OptionalInt and vice-versa.

It's painful because we start to see interface that returns by example OptionalInt while the implementation you want to connect with return an Optional<Integer>.

The only workaround seems to be to use a Stream/IntStream:
 Optional -> OptionalInt
   optional.stream().mapToInt(x -> x).findFirst()
 OptionalInt -> Optional
   optionalInt.stream().boxed().findFirst();

I think, Optional should have the method mapTo*/flatMapTo* and Optional[Primitive] the method boxed().

regards,
Rémi 

----- Mail original -----
> De: "Stuart Marks" <stuart.marks at oracle.com>
> À: "core-libs-dev" <core-libs-dev at openjdk.java.net>
> Envoyé: Vendredi 8 Décembre 2017 01:33:41
> Objet: RFR(s): 8140281 add no-arg Optional.orElseThrow() as preferred alternative to get()

> Hi all,
> 
> Please review this changeset that introduces a new no-arg method orElseThrow()
> to Optional, as a preferred alternative to the get() method.
> 
> Corresponding methods are also added to OptionalDouble, Int, and Long.
> 
> The orElseThrow() method is functionally identical to get(). It has some
> affinity with the existing orElseThrow(exceptionSupplier) method, being
> equivalent to orElseThrow(NoSuchElementException::new).
> 
> The get() method is functionally unchanged. It is NOT being deprecated, although
> some wording in the doc has been added to point to orElseThrow() as the
> "preferred alternative." This is part of a (slow) migration away from
> Optional.get(), which has an obvious, attractive name that is often misused.
> These issues have been discussed on this list previously:
> 
>     http://mail.openjdk.java.net/pipermail/core-libs-dev/2016-April/040484.html
> 
> Please note that much of that discussion was about the then-proposed deprecation
> of Optional.get(), which is NOT part of this proposal. There are no plans to
> deprecate Optional.get() at this time. This proposal ONLY introduces a new
> method orElseThrow() that is identical in function to get().
> 
> Bug report:
> 
>     https://bugs.openjdk.java.net/browse/JDK-8140281
> 
> Webrev:
> 
>     http://cr.openjdk.java.net/~smarks/reviews/8140281/webrev.1/
> 
> Thanks,
> 
> s'marks