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

[Doug Lea]

On 03/27/13 11:45, Joe Bowbeer wrote:
> putIfAbsent was not designed to be compatible with null values. It was designed
> for the null-incompatible ConcurrentMap interface. I don't think a
> null-compatible implementation of CM is possible, BTW.
>

This is what everyone mis-remembers. Somehow I let someone talk
me into not strictly banishing nulls in ConcurrentMap interface
specs, even though some methods are not very useful if they are
allowed, and no actual implementation I know allows them.

The defaults for the new stream-collect-friendly Map methods
preserve this state of affairs.

-Doug