jodd.cache

Class LRUCache<K,V>

java.lang.Object

jodd.cache.AbstractCacheMap<K,V>

jodd.cache.LRUCache<K,V>

All Implemented Interfaces:

Cache<K,V>

public class LRUCache<K,V>
extends AbstractCacheMap<K,V>

LRU (least recently used) cache.

Items are added to the cache as they are accessed; when the cache is full, the least recently used item is ejected. This type of cache is typically implemented as a linked list, so that an item in cache, when it is accessed again, can be moved back up to the head of the queue; items are ejected from the tail of the queue. Cache access overhead is again constant time. This algorithm is simple and fast, and it has a significant advantage over FIFO in being able to adapt somewhat to the data access pattern; frequently used items are less likely to be ejected from the cache. The main disadvantage is that it can still get filled up with items that are unlikely to be reaccessed soon; in particular, it can become useless in the face of scanning type accesses. Nonetheless, this is by far the most frequently used caching algorithm.

Implementation note: unfortunately, it was not possible to have onRemove callback method, since LinkedHashMap has its removal methods private.

Summary for LRU: fast, adaptive, not scan resistant.

Field Summary

Fields inherited from class jodd.cache.AbstractCacheMap

cacheMap, cacheSize, existCustomTimeout, hitCount, missCount, timeout

Constructor Summary

Constructors

Constructor and Description
LRUCache(int cacheSize)
LRUCache(int cacheSize, long timeout) Creates a new LRU cache.

Method Summary

Methods

Modifier and Type	Method and Description
protected int	pruneCache() Prune only expired objects, LinkedHashMap will take care of LRU if needed.
protected boolean	removeEldestEntry(int currentSize) Removes the eldest entry if current cache size exceed cache size.

Methods inherited from class jodd.cache.AbstractCacheMap

clear, get, getCacheSize, getCacheTimeout, getHitCount, getMissCount, isEmpty, isFull, isPruneExpiredActive, iterator, prune, put, put, remove, size

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

LRUCache

public LRUCache(int cacheSize)

LRUCache

public LRUCache(int cacheSize,
        long timeout)

Creates a new LRU cache.

Method Detail

removeEldestEntry

protected boolean removeEldestEntry(int currentSize)

Removes the eldest entry if current cache size exceed cache size.

pruneCache

protected int pruneCache()

Prune only expired objects, LinkedHashMap will take care of LRU if needed.

Specified by:

pruneCache in class AbstractCacheMap<K,V>