A disk store implementation.
As of ehcache-1.2 (v1.41 of this file) DiskStore has been changed to a mix of finer grained locking using synchronized collections and synchronizing on the whole instance, as was the case with earlier versions.
The DiskStore, as of ehcache-1.2.4, supports eviction using an LFU policy, if a maximum disk store size is set. LFU uses statistics held at the Element level which survive moving between maps in the MemoryStore and DiskStores.
@author Adam Murdoch
@author Greg Luck
@author patches contributed: Ben Houston
@version $Id: DiskStore.java 796 2008-10-09 02:39:03Z gregluck $