org.apache.slide.util
Class AbstractObjectCache

java.lang.Object
  |
  +--org.apache.slide.util.AbstractObjectCache

All Implemented Interfaces:

ObjectCache

Direct Known Subclasses:

HashMapObjectCache

public abstract class AbstractObjectCache

extends java.lang.Object

implements ObjectCache

Object cache abstract implementation.

Version:

$Revision: 1.5 $ $Date: 2000/09/26 02:44:28 $

Author:

Remy Maucherat

Field Summary

protected double	cacheHits Number of cache hits.
protected double	cacheRequests Number of cache requests.
protected double	currentHitRatio Current cache hit ratio.
protected static double	DEFAULT_HIT_RATIO Default desired hit ratio.
protected static int	DEFAULT_SIZE Default cache size.
protected double	desiredHitRatio Desired hit ratio.
protected int	initialSize Initial cache size.
protected int	maxSize Maximum cache size.

Constructor Summary

AbstractObjectCache()
Constructor.

AbstractObjectCache(int initialSize, int maxSize, double desiredHitRatio)
Constructor.

Method Summary

abstract void	clear() Clear object cache.
abstract java.lang.Object	get(java.lang.Object key) Get the object associated with the key.
protected abstract int	getSize() Get cache size.
abstract void	put(java.lang.Object key, java.lang.Object value) Add an object to the cache, or overwrite its value.
abstract void	remove(java.lang.Object key) Remove object associated with the given key.
protected abstract void	removeSomeObjects() Removes some elements from the cache.
protected abstract void	resize() Resize cache.
protected void	shouldResize() Is the cache size too small ?

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_SIZE

protected static final int DEFAULT_SIZE

Default cache size.

DEFAULT_HIT_RATIO

protected static final double DEFAULT_HIT_RATIO

Default desired hit ratio.

initialSize

protected int initialSize

Initial cache size.

desiredHitRatio

protected double desiredHitRatio

Desired hit ratio.

maxSize

protected int maxSize

Maximum cache size.

cacheRequests

protected double cacheRequests

Number of cache requests.

cacheHits

protected double cacheHits

Number of cache hits.

currentHitRatio

protected double currentHitRatio

Current cache hit ratio. Equals to cacheHits / cacheRequests, if, and only if cacheRequests >= cache.size(). Otherwise, it's value is not used. If the cache hit ratio, is inferior to the desired hit ratio, the cache grows (unless its maximum size is already reached).

Constructor Detail

AbstractObjectCache

public AbstractObjectCache()

Constructor.

Warning (blinking) : That constructor is to be used really carefully as the cache maximum size is not limited.

AbstractObjectCache

public AbstractObjectCache(int initialSize,
                           int maxSize,
                           double desiredHitRatio)

Constructor.

Parameters:

initialSize - Initial size of the cache

maxSize - Maximum size of the cache

desiredHitRatio - Desired cache hit ratio

Method Detail

get

public abstract java.lang.Object get(java.lang.Object key)

Get the object associated with the key.

Specified by:

get in interface ObjectCache

Parameters:

key - Object's key

Returns:

Object null if there is no object associated with that key in the cache, or the object value otherwise

put

public abstract void put(java.lang.Object key,
                         java.lang.Object value)

Add an object to the cache, or overwrite its value.

Specified by:

put in interface ObjectCache

Parameters:

key - Object's key

object - Object's value

remove

public abstract void remove(java.lang.Object key)

Remove object associated with the given key. Doesn't do anything if the key wasn't associated with any object.

Specified by:

remove in interface ObjectCache

Parameters:

key - Object's key

clear

public abstract void clear()

Clear object cache.

Specified by:

clear in interface ObjectCache

removeSomeObjects

protected abstract void removeSomeObjects()

Removes some elements from the cache. The selection of the objects to remove, along with the number are left to the implementation.

getSize

protected abstract int getSize()

Get cache size.

Returns:

int Current cache size

resize

protected abstract void resize()

Resize cache.

shouldResize

protected void shouldResize()

Is the cache size too small ?