LRUMap的一种： LinkedHashMap原来这么有魅力

http://stackoverflow.com/questions/224868/easy-simple-to-use-lru-cache-in-java

Easy, simple to use LRU cache in java

I know it's simple to implement, but I want to reuse something that already exist.

Problem I want to solve is that I load configuration (from XML so I want to cache them) for different pages, roles, ... so the combination of inputs can grow quite much (but in 99% will not). To handle this 1%, I want to have some max number of items in cache...

Till know I have found org.apache.commons.collections.map.LRUMap in apache commons and it looks fine but want to check also something else. Any recommendations?

 

You can use a LinkedHashMap (Java 1.4+) :
The code from exampledepot.com:
// Create cache
final int MAX_ENTRIES = 100;
Map cache = new LinkedHashMap(MAX_ENTRIES+1, .75F, true) { //true 以访问顺序排列；false 以插入顺序排列
    // This method is called just after a new entry has been added
    public boolean removeEldestEntry(Map.Entry eldest) {
        return size() > MAX_ENTRIES;//删除最老的键值对的条件
    }
};
// Add to cache
Object key = "key";
cache.put(key, object);
// Get object
Object o = cache.get(key);
if (o == null && !cache.containsKey(key)) {
    // Object not in cache. If null is not a possible value in the cache,
    // the call to cache.contains(key) is not needed
}
// If the cache is to be used by multiple threads,
// the cache must be wrapped with code to synchronize the methods
cache = (Map)Collections.synchronizedMap(cache);