Module org.glassfish.hk2.utilities

Package org.glassfish.hk2.utilities.cache

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.

Author:

Jakub Podlesak (jakub.podlesak at oracle.com)

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	LRUHybridCache.CycleHandler<K>	Should a cycle be detected during computation of a value for given key, this interface allows client code to register a callback that would get invoked in such a case.

Constructor Summary

Constructors

Constructor	Description
LRUHybridCache(int maxCacheSize, Computable<K,HybridCacheEntry<V>> computable)	Create new cache with given computable to compute values.
LRUHybridCache(int maxCacheSize, Computable<K,HybridCacheEntry<V>> computable, LRUHybridCache.CycleHandler<K> cycleHandler)	Create new cache with given computable and cycleHandler.

Method Summary

Modifier and Type	Method	Description
void	clear()	Empty the cache.
HybridCacheEntry<V>	compute(K key)	Defines an expensive computation to retrieve value V from key K.
boolean	containsKey(K key)	Returns true if the key has already been cached.
HybridCacheEntry<V>	createCacheEntry(K k, V v, boolean dropMe)	Create cache entry for given values.
int	getMaximumCacheSize()
void	releaseMatching(CacheKeyFilter<K> filter)	This method will remove all cache entries for which this filter matches
void	remove(K key)	Remove given item from the cache.
int	size()	Return the size of the cache

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

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.

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