Is there a SoftHashMap in Java?

I am familiar with two libraries that offer a SoftHashMap implementation:

1. Apache Commons: org.apache.commons.collections.map.ReferenceMap

2. Google Collections: com.google.common.collect.ReferenceMap

Edit (Aug. 2012):

It turns out that currently the best solution are probably Guava 13.0's Cache classes, explained on Guava's Wiki - that's what I'm going to use. It even supports building a SoftHashMap (see CacheBuilder.newBuilder().softKeys()), but it is probably not what you want, as Java expert Jeremy Manson explains (below you'll find the link).

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Not that I know of (Nov. 2008), but you kind find some implementation of SoftHashMap on the net.

Like this one: SoftHashMap or this one.

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Edit (Nov. 2009)
As Matthias mentions in the comments, the Google Guava MapMaker does use SoftReferences:

A ConcurrentMap builder, providing any combination of these features:

• soft or weak keys,

• soft or weak values,
• timed expiration, and
• on-demand computation of values.

As mentioned in this thread, another JSR166y candidate:

jsr166y.ConcurrentReferenceHashMap

It provides an alternative concurrent reference map to the Google implementation (which relies on a background thread to evict entries)

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Edit (August 2012)

The Google implementation uses a background thread only when timed expiration of entries is requested. In particular, it simply uses java.util.Timer, which is not so intrusive as having a separate background thread.

Jeremy Manson recommends, for any cache, using this feature to avoid the dangers of SoftReference: http://jeremymanson.blogspot.de/2009/07/how-hotspot-decides-to-clear_07.html

There's another implementation from Apache Commons, namely org.apache.commons.collections.map.ReferenceMap; it does not support timed removal, but it does support choosing whether keys should be compared by identity or by equality. Moreover, this implementation is not concurrent - it can be made synchronized, but that works less well under accesses from multiple threads.

There is an example implementation in 98 issue of java specialists newsletter