net.sourceforge.rcache
Class WeakCache<K,V>

java.lang.Object
  java.util.AbstractMap<K,V>
      net.sourceforge.rcache.BaseCache<K,V>
          net.sourceforge.rcache.WeakCache<K,V>

Type Parameters:

K - the type of keys maintained by this cache

V - the type of cached values

All Implemented Interfaces:

java.util.Map<K,V>, Cache<K,V>

public class WeakCache<K,V>
extends BaseCache<K,V>

Memory-Sensitive Cache Based on WeakReferences

Entries in a WeakCache will be garbage collected as soon as there are no hard references left.

For certain applications, this garbage collection policy may be too aggressive, and it may be preferable to keep objects in memory until there is really a need to free space. For those cases, SoftCache will be a more sensible option.

Author:

Rodrigo Ruiz

See Also:

WeakReference

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

java.util.AbstractMap.SimpleEntry<K,V>, java.util.AbstractMap.SimpleImmutableEntry<K,V>

Nested classes/interfaces inherited from interface net.sourceforge.rcache.Cache

Cache.Operation

Nested classes/interfaces inherited from interface java.util.Map

java.util.Map.Entry<K,V>

Field Summary

Fields inherited from interface net.sourceforge.rcache.Cache

DEFAULT_CONCURRENCY_LEVEL, DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR

Constructor Summary

WeakCache()
Default constructor.

WeakCache(int initialCapacity)
Creates an instance with a custom initial capacity.

WeakCache(int initialCapacity, float loadFactor)
Creates an instance with a custom initial capacity and load factor.

WeakCache(int initialCapacity, float loadFactor, int concurrencyLevel)
Creates an instance with custom capacity and concurrency level.

Method Summary

protected KeyedReference<K,V>

createRef(K key, V value, java.lang.ref.ReferenceQueue<V> queue) Factory method for creating a new reference instance.

Methods inherited from class net.sourceforge.rcache.BaseCache

clear, entrySet, equals, get, hashCode, purge, put, remove, size, values

Methods inherited from class java.util.AbstractMap

clone, containsKey, containsValue, isEmpty, keySet, putAll, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

WeakCache

public WeakCache()

Default constructor.

Instances created with this constructor will have a small initial capacity and a highly restricted concurrency level.

For concurrent maps, resizing is a costly operation. Whenever possible, it is advised to specify the expected maximum size, in order to minimise the number of resizes.

WeakCache

public WeakCache(int initialCapacity)

Creates an instance with a custom initial capacity.

Parameters:

initialCapacity - The map initial capacity

WeakCache

public WeakCache(int initialCapacity,
                 float loadFactor)

Creates an instance with a custom initial capacity and load factor.

Parameters:

initialCapacity - The map initial capacity

loadFactor - The map load factor

WeakCache

public WeakCache(int initialCapacity,
                 float loadFactor,
                 int concurrencyLevel)

Creates an instance with custom capacity and concurrency level.

The concurrency level is used as a hint to select the internal Map implementation:

• < 0 : Do not care about concurrency. A HashMap will be used.
• = 0 : No concurrent access allowed. A Hashtable will be selected.
• > 0 : A ConcurrentHashMap will be created with the specified concurrency level.

Parameters:

initialCapacity - The map initial capacity

loadFactor - The map load factor

concurrencyLevel - The concurrency level.

Method Detail

createRef

protected final KeyedReference<K,V> createRef(K key,
                                              V value,
                                              java.lang.ref.ReferenceQueue<V> queue)

Factory method for creating a new reference instance.

Specified by:

createRef in class BaseCache<K,V>

Parameters:

key - The key

value - The value

queue - A reference queue

Returns:

A reference instance containing the key and value