您将如何在 Java 中实现 LRU 缓存? [英] How would you implement an LRU cache in Java?

问题描述

请不要说 EHCache 或 OSCache 等.为了这个问题的目的，假设我想仅使用 SDK 来实现我自己的(边做边学).鉴于缓存将用于多线程环境，您会使用哪种数据结构?我已经使用 LinkedHashMap 和Collections#synchronizedMap，但我很好奇是否有任何新的并发集合是更好的候选者.

Please don't say EHCache or OSCache, etc. Assume for purposes of this question that I want to implement my own using just the SDK (learning by doing). Given that the cache will be used in a multithreaded environment, which datastructures would you use? I've already implemented one using LinkedHashMap and Collections#synchronizedMap, but I'm curious if any of the new concurrent collections would be better candidates.

更新:我刚刚阅读了Yegge 的最新消息 当我发现这个金块时:

UPDATE: I was just reading through Yegge's latest when I found this nugget:

如果您需要恒定时间访问并想要维护插入顺序，那么您不能比 LinkedHashMap 做得更好，这是一个真正美妙的数据结构.它可能更精彩的唯一方法是如果有一个并发版本.但是唉.

If you need constant-time access and want to maintain the insertion order, you can't do better than a LinkedHashMap, a truly wonderful data structure. The only way it could possibly be more wonderful is if there were a concurrent version. But alas.

在使用我上面提到的 LinkedHashMap + Collections#synchronizedMap 实现之前，我的想法几乎完全相同.很高兴知道我没有忽略一些东西.

I was thinking almost exactly the same thing before I went with the LinkedHashMap + Collections#synchronizedMap implementation I mentioned above. Nice to know I hadn't just overlooked something.

根据目前的答案，对于高并发 LRU 来说，我最好的选择是扩展 ConcurrentHashMap 使用一些与 LinkedHashMap 使用的相同的逻辑.

Based on the answers so far, it sounds like my best bet for a highly concurrent LRU would be to extend ConcurrentHashMap using some of the same logic that LinkedHashMap uses.

推荐答案

如果我今天从头再来一次，我会使用 Guava 的 CacheBuilder.

If I were doing this again from scratch today, I'd use Guava's CacheBuilder.

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