Java Collection实现了元素的超时

Question

Is there some collection implementation supporting expiration of the elements.

For example:

Collection<User> cachedUsers = new ExpirableList<User>(10000);

where

public ExpirableList(final long timeout){...}

And after given time ( 10000ms in this particular example), added elements will be removed from the collection. By using this, we will prevent overflow of our cachedUsers collection.

Answer 1

Yes, Guava supports a cache with timed expiration. See Guava Explained's page on caches .

An alternative is an LRU (least-recently used) cache that disposes of the oldest accessed element when a new element is inserted.

Answer 2

目前还不清楚你是如何尝试使用该系列的，但是Guava的CacheBuilder可能对你有所帮助。

Answer 3

Another alternative is ExpiringMap :

Map<String, User> users = ExpiringMap.builder()
  .expiration(10, TimeUnit.SECONDS)
  .build();

Answer 4

You could implement this by writing a wrapper for, say, a TreeMap where you let the insertion time be the key. On each insert, you could drop the head list which has "timed out".

Using insertion time as an indication on whether or not in should be dropped seems like a bad idea though. It seems better to go with some LRU (least recently used) cache for instance. Such caches are readily available in libraries such as EHCache for instance. Don't reinvent the wheel.

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