用LinkedHashMap实现的简单LRU Cache

iteye_11539

于 2011-10-08 12:23:00 发布

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本文介绍了一种使用LinkedHashMap实现的缓存管理系统，该系统能够自动移除最旧的条目以保持缓存大小不超过预设的最大容量。文章还讨论了如何通过同步方法来确保缓存在多线程环境下的安全性。

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// 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);