Request for review: 7123229: (coll) EnumMap.containsValue(null) returns true

[Alan Bateman]

Neil - are you still planning to push this to jdk8/tl? As it's 
regression, albeit small, it seems like a good candidate for jdk7u too.

-Alan.

On 10/01/2012 01:05, Neil Richards wrote:
> Hi all,
> When proposing the change for 6312706 [1], I erroneously managed to
> convince myself (and others!) that it would be safe to use 'new
> Integer(0)' for java.util.EnumMap.NULL (the object used to mark null
> values for entries in the map) [2].
>
> This was on the basis that I thought it was only compared by identity.
> However, on closer inspection, this turns out not to be the case.
>
> 7123229 was raised to report the bug that was introduced based on this
> invalid assumption.
>
> I've created a webrev with a suggested fix for 7123229 [3], which
> changes NULL to be an Object which:
>        * will only return 'true' from equals(Object) for itself
>        * returns 0 from hashCode()
>
> For good measure, it also returns a sensible value from toString().
>
> Please review this fix and let me know your thoughts,
> Thanks,
> Neil
>
> [1] http://hg.openjdk.java.net/jdk7/tl/jdk/rev/c1e87a18e46a
> [2] http://mail.openjdk.java.net/pipermail/core-libs-dev/2011-March/006353.html
> [3] http://cr.openjdk.java.net/~ngmr/7123229/webrev.00/
>