在java中简单易用的LRU缓存

问题描述

我知道实现起来很简单，但我想重用已经存在的东西.

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

我想解决的问题是，我为不同的页面、角色加载配置(从 XML，所以我想缓存它们)，所以输入的组合可以增长很多(但 99% 不会).为了处理这 1%，我希望缓存中有一些最大项目数...

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...

直到知道我在 apache commons 中找到了 org.apache.commons.collections.map.LRUMap，它看起来不错，但还想检查其他东西.有什么推荐吗?

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?

推荐答案

您可以使用 LinkedHashMap (Java 1.4+) :

You can use a LinkedHashMap (Java 1.4+) :

// Create cache
final int MAX_ENTRIES = 100;
Map cache = new LinkedHashMap(MAX_ENTRIES+1, .75F, true) {
    // This method is called just after a new entry has been added
    public boolean removeEldestEntry(Map.Entry eldest) {
        return size() > MAX_ENTRIES;
    }
};

// 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);

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