Class LRUHybridCache<K,V>

java.lang.Object
org.glassfish.hk2.utilities.cache.LRUHybridCache<K,V>
Type Parameters:
K - The type for the keys in the cache
V - The type for the values in the cache
All Implemented Interfaces:
Computable<K,HybridCacheEntry<V>>

public class LRUHybridCache<K,V> extends Object implements Computable<K,HybridCacheEntry<V>>
Hybrid cache that allows explicit removals of included entries as well as implicit removal of entries that have been least recently accessed. The implicit removal happens only in case the internal cache runs out of space. Maximum number of items that can be kept in the cache is invariant for a single cache instance, and can be set in the cache constructor. The cache deals with HybridCacheEntry items than could even instruct the cache to drop them as they get computed. The cache will still make sure such items get computed just once in given time (based on computation length) for given key. Desired value will only be computed once and computed value stored in the cache. The implementation is based on an example from the "Java Concurrency in Practice" book authored by Brian Goetz and company.
  • Field Details

  • Constructor Details

    • LRUHybridCache

      public LRUHybridCache(int maxCacheSize, Computable<K,HybridCacheEntry<V>> computable)
      Create new cache with given computable to compute values.
      Parameters:
      maxCacheSize - The maximum number of entries in the cache
      computable - The thing that can create the entry
    • LRUHybridCache

      public LRUHybridCache(int maxCacheSize, Computable<K,HybridCacheEntry<V>> computable, LRUHybridCache.CycleHandler<K> cycleHandler)
      Create new cache with given computable and cycleHandler.
      Parameters:
      maxCacheSize - The maximum number of entries in the cache
      computable - The thing that can create the entry
      cycleHandler - What to do if a cycle is detected
  • Method Details

    • createCacheEntry

      public HybridCacheEntry<V> createCacheEntry(K k, V v, boolean dropMe)
      Create cache entry for given values.
      Parameters:
      k - cache entry key.
      v - cache entry value.
      dropMe - should this entry be kept in the cache this must be set to false.
      Returns:
      an instance of cache entry.
    • compute

      public HybridCacheEntry<V> compute(K key)
      Description copied from interface: Computable
      Defines an expensive computation to retrieve value V from key K.
      Specified by:
      compute in interface Computable<K,V>
      Parameters:
      key - input data.
      Returns:
      output from the computation.
    • clear

      public void clear()
      Empty the cache.
    • size

      public int size()
      Return the size of the cache
      Returns:
      The current size of the cache
    • getMaximumCacheSize

      public int getMaximumCacheSize()
    • containsKey

      public boolean containsKey(K key)
      Returns true if the key has already been cached.
      Parameters:
      key -
      Returns:
      true if given key is present in the cache.
    • remove

      public void remove(K key)
      Remove given item from the cache.
      Parameters:
      key - item key.
    • removeLRUItem

      private void removeLRUItem()
      Remove least recently used item form the cache. No checks are done here. The method just tries to remove the least recently used cache item. An exception will be thrown if the cache is empty.
    • releaseMatching

      public void releaseMatching(CacheKeyFilter<K> filter)
      This method will remove all cache entries for which this filter matches
      Parameters:
      filter - Entries in the cache that match this filter will be removed from the cache. If filter is null nothing will be removed from the cache