The ReferenceMap in the CVS has the ability to weakly reference keys in a variety of ways. But it doesn't use == testing. Really ReferenceMap could do with being a subclass of HashedMap, then adding Identity behaviour would be easy.
HashedMap has worked out really well so far, and I added a load more override possibilities tonight, so it should cover most subclass requirements now.. Stephen ----- Original Message ----- From: "Brian S O'Neill" <[EMAIL PROTECTED]> > The "IdentityMap" caught my attention. I wrote a map with the same name > awhile back which had one extra feature. The keys were weakly > referenced. I think the name "WeakIdentityMap" is more sensible. The > implementation would clean out cleared entires as they were discovered > and before expansions. If space is freed up, then the expansion in > canceled. This map can be safely used in place of IdentityMap, but it > may have extra performance and storage overhead. > > Anyhow, I'm wondering if you think that the extensible HashedMap > contains enough "override" points to make this sort of map possible > without having to implement from WeakIdentityMap from scratch. I think > all the necessary override points are there, I'll just have to see if it > works. > > http://teatrove.sourceforge.net/javadoc/com/go/trove/util/IdentityMap.html > > Stephen Colebourne wrote: > > >A number of new classes now form a hierarchy in the map subpackage: > > > >HashedMap (general hash map) > > > >IdentityMap extends HashedMap (uses ==) > > > >LinkedMap extends HashedMap (insertion order) > > > >LRUMap extends LinkedMap (access order, drops oldest) > > > > > >Is everyone happy with this hierarchy? > >Should LRUMap (access order) extend LinkedMap (insertion order) (lots of > >code shared)? > >Should there be an AbstractHashedMap class, rather than all extending > >HashedMap? > > > >We're going to have to live with this so it needs to be right.....;-) > > > >Also, should caching and reusing of previous MapEntry objects be part of the > >default implementations? > > > >Finally, I think that StaticBucketMap and ReferenceMap don't benefit from > >extending HashedMap, but if someone wants to confirm or deny this they're > >most welcome :-0 > > > >Stephen > > > > > >--------------------------------------------------------------------- > >To unsubscribe, e-mail: [EMAIL PROTECTED] > >For additional commands, e-mail: [EMAIL PROTECTED] > > > > > > > > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
