A cache storage that implements a two-level Most Recently Used cache. In the
first level, items are strongly referenced up to the specified maximum. When
the maximum is exceeded, the least recently used item is moved into the
second level cache, where they are softly referenced, up to another
specified maximum. When the second level maximum is also exceeded, the least
recently used item is discarded altogether. This cache storage is a
generalization of both
- the effect of both of them can be achieved by
setting one maximum to zero and the other to the largest positive integer.
On the other hand, if you wish to use this storage in a strong-only mode, or
in a soft-only mode, you might consider using
instead, as they can be used by
concurrently without any synchronization on a 5.0 or
This class is NOT
thread-safe. If it's accessed from multiple
threads concurrently, proper synchronization must be provided by the callers.
, the natural user of this class provides the
necessary synchronizations when it uses the class.
Also you might consider whether you need this sort of a mixed storage at all
in your solution, as in most cases SoftCacheStorage can also be sufficient.
SoftCacheStorage will use Java soft references, and they already use access
timestamps internally to bias the garbage collector against clearing
recently used references, so you can get reasonably good (and
memory-sensitive) most-recently-used caching through