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I need to cache some objects with fairly heavy creation times, and I need exactly-once creation semantics. It should be possible to create objects for different CacheKeys concurrently. I think I need something that (under the hood) does something like this:
ConcurrentHashMap<CacheKey, Future<HeavyObject>>
Are there any existing open-source implementations of this that I can re-use ?
Have you looked at Guava‘s
MapMakerclass? I think it will do everything you need – although instead of providing aFuture, you give the class aFunction<? super K, ? extends V>which is used to compute the value.Looking back over your post, if you really need to put values in there rather than computing them, it won’t work as well – but I’ll leave the suggestion here in case a computing map is okay for you.