org.apache.flex.utils

Class IntMapLRUCache

java.lang.Object

org.apache.flex.utils.IntMapLRUCache

public abstract class IntMapLRUCache
extends Object

Caching data structure that uses a Least Recently Used (LRU) algorithm. This cache has a max size associated with it that is used to determine when objects should be purged from the cache. Once the max size is reached, the least recently used element will be purged.

This class is thread-safe.

Constructor Summary

Constructors

Constructor and Description
IntMapLRUCache(int initialSize, int maxSize) Create a new LRU cache.
IntMapLRUCache(int initialSize, int maxSize, int purgeSize) Create a new LRU cache.

Method Summary

Methods

Modifier and Type	Method and Description
abstract Object	fetch(int key)
int	firstKey()
Object	get(int key) Retrieve an object from the cache using the specified key.
int	getMaxSize() Returns the number of elements that this cache can hold.
int	getPurgeSize() Returns the number of LRU elements to purge when the max size is reached.
protected void	handleLRUElementPurged(int key, Object value) Handler hook to signal subclasses that the LRU element has been purged from the cache.
Object	put(int key, Object value) Insert an object into the cache.
void	remove(int key) Remove an object from the cache.
void	setSize(int size)
int	size() Returns the number of elements currently in the cache.

Methods inherited from class java.lang.Object

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

Constructor Detail

IntMapLRUCache

public IntMapLRUCache(int initialSize,
              int maxSize)

Create a new LRU cache.

Parameters:

initialSize - the initial size of the IntMap

maxSize - the maximum number of elements this cache can hold before purging LRU elements.

IntMapLRUCache

public IntMapLRUCache(int initialSize,
              int maxSize,
              int purgeSize)

Create a new LRU cache. This constructor takes a purgeSize parameter that is used to increase the number of LRU elements to when the cache exceeds its max size. Increasing the purge size can reduce the overhead of using the cache if the cache size is maxed out frequently.

Parameters:

initialSize - the initial size of the IntMap

maxSize - the maximum number of elements this cache can hold before purging LRU elements.

purgeSize - the number of LRU elements to purge once the max size is exceeded.

Method Detail

get

public Object get(int key)

Retrieve an object from the cache using the specified key. Use of this method will make the retrieved object the most recently used object.

firstKey

public int firstKey()

put

public Object put(int key,
         Object value)

Insert an object into the cache.

remove

public void remove(int key)

Remove an object from the cache.

setSize

public void setSize(int size)

size

public int size()

Returns the number of elements currently in the cache.

getMaxSize

public int getMaxSize()

Returns the number of elements that this cache can hold. Once more than this number of elements is added to the cache, the least recently used element will automatically be removed.

getPurgeSize

public int getPurgeSize()

Returns the number of LRU elements to purge when the max size is reached.

handleLRUElementPurged

protected void handleLRUElementPurged(int key,
                          Object value)

Handler hook to signal subclasses that the LRU element has been purged from the cache. This method is triggered when the cache's max size has been exceeded and the LRU element must be removed from the cache. This method is invoked after the LRU element has been removed from the cache.

Parameters:

key - the insertion key that was originally used to add value to the cache.

value - the value element bound to the key.

fetch

public abstract Object fetch(int key)