hg: lambda/lambda/jdk: bug fixes and unit test for Map Defaults

[Doug Lea]

On 03/28/13 00:51, Joe Bowbeer wrote:
> The way I'm interpreting this is:
>
> 1. ConcurrentMap effectively prohibits nulls (feel free to make analogies with
> effective thread safety;)

No, it has exactly the same issues as the added Map methods.
If you use it with a null-value-accepting Map, then it
does something that meets spec, but that something might not
be what you have in mind.

Backing up: the reason these are added to Map is that without
them, streams can't reasonably implement map-related collect
operations. Would you rather we kill them? And it is
not just Streams; no one else can write them either without
knowing exactly which concrete Map class they have.

This is one of the reasons I ranted so much last year about
why banishing nulls from streams was simplest path to
API sanity. That is, if we can't banish them from
Collections/Maps, we could at least do so as stream
sources/destinations. Given that we didn't do this,
there's a continual set of subsidiary issues like this
one.

-Doug