org.apache.commons.collections.list
Class NodeCachingLinkedList

java.lang.Object
  org.apache.commons.collections.list.AbstractLinkedList
      org.apache.commons.collections.list.NodeCachingLinkedList

All Implemented Interfaces:

java.io.Serializable, java.lang.Iterable, java.util.Collection, java.util.List

public class NodeCachingLinkedList
extends AbstractLinkedList
implements java.io.Serializable

A List implementation that stores a cache of internal Node objects in an effort to reduce wasteful object creation.

A linked list creates one Node for each item of data added. This can result in a lot of object creation and garbage collection. This implementation seeks to avoid that by maintaining a store of cached nodes.

This implementation is suitable for long-lived lists where both add and remove are used. Short-lived lists, or lists which only grow will have worse performance using this class.

Note that this implementation is not synchronized.

Since:

Commons Collections 3.0

Version:

$Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $

Author:

Jeff Varszegi, Rich Dougherty, Phil Steitz, Stephen Colebourne

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.commons.collections.list.AbstractLinkedList

AbstractLinkedList.LinkedListIterator, AbstractLinkedList.LinkedSubList, AbstractLinkedList.LinkedSubListIterator, AbstractLinkedList.Node

Field Summary

protected int	cacheSize The size of the cache.
protected static int	DEFAULT_MAXIMUM_CACHE_SIZE The default value for maximumCacheSize.
protected AbstractLinkedList.Node	firstCachedNode The first cached node, or null if no nodes are cached.
protected int	maximumCacheSize The maximum size of the cache.

Fields inherited from class org.apache.commons.collections.list.AbstractLinkedList

header, modCount, size

Constructor Summary

NodeCachingLinkedList()
Constructor that creates.

NodeCachingLinkedList(java.util.Collection coll)
Constructor that copies the specified collection

NodeCachingLinkedList(int maximumCacheSize)
Constructor that species the maximum cache size.

Method Summary

protected void	addNodeToCache(AbstractLinkedList.Node node) Adds a node to the cache, if the cache isn't full.
protected AbstractLinkedList.Node	createNode(java.lang.Object value) Creates a new node, either by reusing one from the cache or creating a new one.
protected int	getMaximumCacheSize() Gets the maximum size of the cache.
protected AbstractLinkedList.Node	getNodeFromCache() Gets a node from the cache.
protected boolean	isCacheFull() Checks whether the cache is full.
protected void	removeAllNodes() Removes all the nodes from the list, storing as many as required in the cache for reuse.
protected void	removeNode(AbstractLinkedList.Node node) Removes the node from the list, storing it in the cache for reuse if the cache is not yet full.
protected void	setMaximumCacheSize(int maximumCacheSize) Sets the maximum size of the cache.
protected void	shrinkCacheToMaximumSize() Reduce the size of the cache to the maximum, if necessary.

Methods inherited from class org.apache.commons.collections.list.AbstractLinkedList

add, add, addAll, addAll, addFirst, addLast, addNode, addNodeAfter, addNodeBefore, clear, contains, containsAll, createHeaderNode, createSubListIterator, createSubListListIterator, doReadObject, doWriteObject, equals, get, getFirst, getLast, getNode, hashCode, indexOf, init, isEmpty, isEqualValue, iterator, lastIndexOf, listIterator, listIterator, remove, remove, removeAll, removeFirst, removeLast, retainAll, set, size, subList, toArray, toArray, toString, updateNode

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_MAXIMUM_CACHE_SIZE

protected static final int DEFAULT_MAXIMUM_CACHE_SIZE

The default value for maximumCacheSize.

See Also:

Constant Field Values

firstCachedNode

protected transient AbstractLinkedList.Node firstCachedNode

The first cached node, or null if no nodes are cached. Cached nodes are stored in a singly-linked list with next pointing to the next element.

cacheSize

protected transient int cacheSize

The size of the cache.

maximumCacheSize

protected int maximumCacheSize

The maximum size of the cache.

Constructor Detail

NodeCachingLinkedList

public NodeCachingLinkedList()

Constructor that creates.

NodeCachingLinkedList

public NodeCachingLinkedList(java.util.Collection coll)

Constructor that copies the specified collection

Parameters:

coll - the collection to copy

NodeCachingLinkedList

public NodeCachingLinkedList(int maximumCacheSize)

Constructor that species the maximum cache size.

Parameters:

maximumCacheSize - the maximum cache size

Method Detail

getMaximumCacheSize

protected int getMaximumCacheSize()

Gets the maximum size of the cache.

Returns:

the maximum cache size

setMaximumCacheSize

protected void setMaximumCacheSize(int maximumCacheSize)

Sets the maximum size of the cache.

Parameters:

maximumCacheSize - the new maximum cache size

shrinkCacheToMaximumSize

protected void shrinkCacheToMaximumSize()

Reduce the size of the cache to the maximum, if necessary.

getNodeFromCache

protected AbstractLinkedList.Node getNodeFromCache()

Gets a node from the cache. If a node is returned, then the value of cacheSize is decreased accordingly. The node that is returned will have null values for next, previous and element.

Returns:

a node, or null if there are no nodes in the cache.

isCacheFull

protected boolean isCacheFull()

Checks whether the cache is full.

Returns:

true if the cache is full

addNodeToCache

protected void addNodeToCache(AbstractLinkedList.Node node)

Adds a node to the cache, if the cache isn't full. The node's contents are cleared to so they can be garbage collected.

Parameters:

node - the node to add to the cache

createNode

protected AbstractLinkedList.Node createNode(java.lang.Object value)

Creates a new node, either by reusing one from the cache or creating a new one.

Overrides:

createNode in class AbstractLinkedList

Parameters:

value - value of the new node

Returns:

the newly created node

removeNode

protected void removeNode(AbstractLinkedList.Node node)

Removes the node from the list, storing it in the cache for reuse if the cache is not yet full.

Overrides:

removeNode in class AbstractLinkedList

Parameters:

node - the node to remove

removeAllNodes

protected void removeAllNodes()

Removes all the nodes from the list, storing as many as required in the cache for reuse.

Overrides:

removeAllNodes in class AbstractLinkedList