JEP 269: Convenience Factory Methods for Collections

Stephen Colebourne scolebourne at
Wed Oct 7 09:30:27 UTC 2015

On 7 October 2015 at 01:13, Stuart Marks <stuart.marks at> wrote:
> My question is, is this enough of a problem that we should allow nulls in
> these collections? I would prefer not to do this, but if there is evidence
> that this would be a mistake, I'd like to hear it.
> And if disallowing nulls will cause developers to create things like
> Map<K,Optional<V>>, are we ok with that, and are developers ok with that?

Given what we know now vs when the collections library ws created, I
think it would be a mistake to allow nulls. Developers that
desperately want null in there have other mechanisms to achieve that,
not just Optional. I too would argue against Optional in collections,
at least until value types exist, but thats a social discussion, not
one that can be controlled.


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