Cache

A Cache is similar to ConcurrentMap, but not quite the same. The most fundamental difference is that a ConcurrentMap persists all elements that are added to it until they are explicitly removed. A Cache on the other hand is generally configured to evict entries automatically, in order to constrain its memory footprint. In some cases a LoadingCache or AsyncLoadingCache can be useful even if it doesn't evict entries, due to its automatic cache loading.

Caffeine provide flexible construction to create a cache with a combination of the following features:

• automatic loading of entries into the cache, optionally asynchronously
• least-recently-used eviction when a maximum size is exceeded
• time-based expiration of entries, measured since last access or last write
• keys automatically wrapped in weak references
• values automatically wrapped in weak or soft references
• notification of evicted (or otherwise removed) entries
• writes propagated to an external resource
• accumulation of cache access statistics