Guava
Caffeine provides an adapter to expose its caches using Guava's interfaces. These adapters provide the same API contract with the implementation caveats below. Where possible Guava like behavior is emulated and validated with a port of Guava's test suite.
When transitioning to Caffeine's interfaces, please note that while the two caches have similar method names the behavior may be slightly different. Please consult the JavaDoc to compare usages more thoroughly.
Guava will evict prior to reaching the maximum size whereas Caffeine will evict once the threshold has been crossed.
Guava converts immediate expiration (expireAfterAccess(0, timeUnit) and
expireAfterWrite(0, timeUnit)) into the setting maximum size equals zero. This results in the
removal notification supplying the size as the cause for removal instead of expiration. Caffeine
correctly identifies expiration as the removal cause.
Guava will ignore entries during invalidation while they are still being computed. In Caffeine each entry being invalidated will block the caller until it has finished computing and will then be removed. If an asynchronous cache is used instead then invalidation is non-blocking as the incomplete future will be removed and the removal notification delegated to the computing thread.
Guava processes removal notifications from a queue that any calling thread may take from. Caffeine
delegates to the configured executor (default: ForkJoinPool.commonPool()).
Guava recomputes an entry on the thread requesting a refresh. Caffeine delegates to the configured
executor (default: ForkJoinPool.commonPool()).
Guava throws an exception when a null value has been computed and retains the entry if due to a
refresh. Caffeine returns the null value and, if the computation was due to a refresh, removes the
entry. If the Guava adapters are used, Caffeine will behave as Guava does if built with a Guava
CacheLoader.
Guava's CacheStats.loadExceptionCount() and CacheStats.loadExceptionRate() are renamed to
CacheStats.loadFailureCount() and CacheStats.loadFailureRate() respectively in Caffeine. This
change is due to null computed values being treated as load failures and not as exceptions.
Caffeine does not provide compatibility due to those platforms not supporting Java 8.
ConcurrentLinkedHashMap requires a minimum weight of 1. Like Guava, Caffeine allows a minimum
weight of 0 to indicate that the entry will not be evicted due to a size-based policy.
ConcurrentLinkedHashMap processes eviction notifications from a queue that any calling thread may
take from. Caffeine delegates to the configured executor (default: ForkJoinPool.commonPool()).
ConcurrentLinkedHashMap retains the entries and discards the eviction order when serializing.
Caffeine, like Guava, retains only the configuration and no data.
