[Jakarta Commons] 使用LRUMap

http://www.blogjava.net/zJun/archive/2006/07/31/61015.html

使用过开源缓存包(如:EHCache)都知道，缓存策略中主要分为FIFO,LRU,LFU等几种。而Jakarta Commons中提供的 org.apache.commons.collections.map.LRUMap 可用来保存最近使用的几条记录，提供了LRU(Least Recently Used)缓存策略的实现。

具体使用方法如下:

import java.util.Map; import org.apache.commons.collections.map.LRUMap; LRUMap cache = new LRUMap( 5 ); // Populate the cache with 5 stock prices cache.put( " MSFT " , new Float( 0.03 ) ); cache.put( " TSC " , new Float( 0.001 ) ); cache.put( " LU " , new Float( 23.30 ) ); cache.put( " CSCO " , new Float( 242.20 ) ); cache.put( " P " , new Float( 10.23 ) ); // Now use some of the entries in the cache Float cscoPrice = (Float) cache.get( " CSCO " ); Float msPrice = (Float) cache.get( " MSFT " ); Float tscPrice = (Float) cache.get( " TSC " ); Float luPrice = (Float) cache.get( " LU " ); Float pPrice = (Float) cache.get( " P " ); Float msPrice2 = (Float) cache.get( " MSFT " ); // Add another price to the Map, this should kick out the LRU item. cache.put( " AA " , new Float( 203.20 ) ); 

此时,缓存中的元素为:

[CSCO]
[MSFT]
[TSC]
[LU]
[P]
[AA]

由于LRU最近没有被访问,所以当AA加入时,由于超过了缓存的最大容量(5),所以被剔除了缓存.