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git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/collections/trunk@130921 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Stephen Colebourne 2003-01-07 23:40:57 +00:00
parent b5f981ff98
commit a11c82f3bc
2 changed files with 300 additions and 177 deletions
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59
src/java/org/apache/commons/collections/CommonsLinkedList.java
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@ -1,3 +1,56 @@
/* ====================================================================
* The Apache Software License, Version 1.1
*
* Copyright (c) 2003 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowlegement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowlegement may appear in the software itself,
* if and wherever such third-party acknowlegements normally appear.
*
* 4. The names "The Jakarta Project", "Commons", and "Apache Software
* Foundation" must not be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact apache@apache.org.
*
* 5. Products derived from this software may not be called "Apache"
* nor may "Apache" appear in their names without prior written
* permission of the Apache Software Foundation.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*/
package org.apache.commons.collections;
import java.io.IOException;
@ -19,10 +72,12 @@ import java.util.NoSuchElementException;
* of {@link java.util.LinkedList}, but which provides a more open interface for
* subclasses to extend.
*
* @since 2.2
* @author <a href="mailto:rich@rd.gen.nz">Rich Dougherty</a>
* @version $Revision: 1.2 $ $Date: 2003/01/07 23:40:55 $
*/
class CommonsLinkedList extends LinkedList
implements List, Serializable {
implements List, Serializable {
/*
* Implementation notes:
@ -232,7 +287,7 @@ class CommonsLinkedList extends LinkedList
private static final long serialVersionUID = 1L;
/**
* A {@link Node} which ndicates the start and end of the list and does not
* A {@link Node} which indicates the start and end of the list and does not
* hold a value. The value of <code>next</code> is the first item in the
* list. The value of of <code>previous</code> is the last item in the list.
*/

418
src/java/org/apache/commons/collections/NodeCachingLinkedList.java
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@ -1,175 +1,243 @@
package org.apache.commons.collections;
import java.util.Collection;
/**
* A linked list implementation that caches the nodes used internally to prevent
* unnecessary object creates and deletion. This should result in a performance
* improvement.
*
* @author Jeff Varszegi
* @author <a href="mailto:rich@rd.gen.nz">Rich Dougherty</a>
*/
public class NodeCachingLinkedList extends CommonsLinkedList {
private static final long serialVersionUID = 1;
/**
* The default value for {@link #maximumCacheSize}.
*/
private static final int DEFAULT_MAXIMUM_CACHE_SIZE = 20;
/**
* The first cached node, or <code>null</code> if no nodes are cached.
* Cached nodes are stored in a singly-linked list with {@link Node#next}
* pointing to the next element.
*/
private transient Node firstCachedNode;
/**
* The size of the cache.
*/
private transient int cacheSize = 0;
/**
* The maximum size of the cache.
*/
private int maximumCacheSize = DEFAULT_MAXIMUM_CACHE_SIZE;
public NodeCachingLinkedList() {
super();
}
public NodeCachingLinkedList(Collection c) {
super(c);
}
public NodeCachingLinkedList(int maximumCacheSize) {
super();
this.maximumCacheSize = maximumCacheSize;
}
// Cache operations
/**
* Gets the maximum size of the cache.
*/
public int getMaximumCacheSize() {
return maximumCacheSize;
}
/**
* Sets the maximum size of the cache.
*/
public void setMaximumCacheSize(int maximumCacheSize) {
this.maximumCacheSize = maximumCacheSize;
shrinkCacheToMaximumSize();
}
/**
* Reduce the size of the cache to the maximum, if necessary.
*/
private void shrinkCacheToMaximumSize() {
// Rich Dougherty: This could be more efficient.
while (cacheSize > maximumCacheSize) {
getNodeFromCache();
}
}
/**
* Gets a node from the cache. If a node is returned, then the value of
* {@link #cacheSize} is decreased accordingly. The node that is returned
* will have <code>null</code> values for next, previous and element.
*
* @return A node, or <code>null</code> if there are no nodes in the cache.
*/
private Node getNodeFromCache() {
if (cacheSize == 0) {
return null;
}
Node cachedNode = firstCachedNode;
firstCachedNode = cachedNode.next;
cachedNode.next = null; // This should be changed anyway, but defensively
// set it to null.
cacheSize--;
return cachedNode;
}
private boolean cacheFull() {
return cacheSize >= maximumCacheSize;
}
/**
* 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.
*/
private void addNodeToCache(Node node) {
if (cacheFull()) {
// Don't cache the node.
return;
}
// Clear the node's contents and add it to the cache.
Node nextCachedNode = firstCachedNode;
node.previous = null;
node.next = nextCachedNode;
node.element = null;
firstCachedNode = node;
cacheSize++;
}
// Node operations
/**
* Create a node, getting it from the cache if possible.
*/
protected Node createNode() {
Node cachedNode = getNodeFromCache();
if (cachedNode == null) {
return super.createNode();
} else {
return cachedNode;
}
}
/**
* Create a node, getting it from the cache if possible.
*/
protected Node createNode(Node next, Node previous, Object element) {
Node cachedNode = getNodeFromCache();
if (cachedNode == null) {
return super.createNode(next, previous, element);
} else {
cachedNode.next = next;
cachedNode.previous = previous;
cachedNode.element = element;
return cachedNode;
}
}
/**
* Calls the superclass' implementation then calls
* {@link #addNodeToCache(Node)} on the node which has been removed.
*
* @see org.apache.commons.collections.CommonsLinkedList#removeNode(Node)
*/
protected void removeNode(Node node) {
super.removeNode(node);
addNodeToCache(node);
}
protected void removeAllNodes() {
// Add the removed nodes to the cache, then remove the rest.
// We can add them to the cache before removing them, since
// {@link CommonsLinkedList.removeAllNodes()} removes the
// nodes by removing references directly from {@link #marker}.
int numberOfNodesToCache = Math.min(size, maximumCacheSize - cacheSize);
Node node = marker.next;
for (int currentIndex = 0; currentIndex < numberOfNodesToCache; currentIndex++) {
Node oldNode = node;
node = node.next;
addNodeToCache(oldNode);
}
super.removeAllNodes();
}
}
/* ====================================================================
* The Apache Software License, Version 1.1
*
* Copyright (c) 2002-2003 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowlegement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowlegement may appear in the software itself,
* if and wherever such third-party acknowlegements normally appear.
*
* 4. The names "The Jakarta Project", "Commons", and "Apache Software
* Foundation" must not be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact apache@apache.org.
*
* 5. Products derived from this software may not be called "Apache"
* nor may "Apache" appear in their names without prior written
* permission of the Apache Software Foundation.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*/
package org.apache.commons.collections;
import java.util.Collection;
/**
* A linked list implementation that caches the nodes used internally to prevent
* unnecessary object creates and deletion. This should result in a performance
* improvement.
*
* @since 2.2
* @author Jeff Varszegi
* @author <a href="mailto:rich@rd.gen.nz">Rich Dougherty</a>
* @version $Revision: 1.3 $ $Date: 2003/01/07 23:40:57 $
*/
public class NodeCachingLinkedList extends CommonsLinkedList {
private static final long serialVersionUID = 1;
/**
* The default value for {@link #maximumCacheSize}.
*/
private static final int DEFAULT_MAXIMUM_CACHE_SIZE = 20;
/**
* The first cached node, or <code>null</code> if no nodes are cached.
* Cached nodes are stored in a singly-linked list with {@link Node#next}
* pointing to the next element.
*/
private transient Node firstCachedNode;
/**
* The size of the cache.
*/
private transient int cacheSize = 0;
/**
* The maximum size of the cache.
*/
private int maximumCacheSize = DEFAULT_MAXIMUM_CACHE_SIZE;
/**
* Constructor.
*/
public NodeCachingLinkedList() {
super();
}
/**
* Constructor that copies the specified collection
*
* @param coll the collection to copy
*/
public NodeCachingLinkedList(Collection coll) {
super(coll);
}
/**
* Constructor that species the maximum cache size.
*
* @param maximumCacheSize the maximum cache size
*/
public NodeCachingLinkedList(int maximumCacheSize) {
super();
this.maximumCacheSize = maximumCacheSize;
}
// Cache operations
/**
* Gets the maximum size of the cache.
*/
public int getMaximumCacheSize() {
return maximumCacheSize;
}
/**
* Sets the maximum size of the cache.
*/
public void setMaximumCacheSize(int maximumCacheSize) {
this.maximumCacheSize = maximumCacheSize;
shrinkCacheToMaximumSize();
}
/**
* Reduce the size of the cache to the maximum, if necessary.
*/
private void shrinkCacheToMaximumSize() {
// Rich Dougherty: This could be more efficient.
while (cacheSize > maximumCacheSize) {
getNodeFromCache();
}
}
/**
* Gets a node from the cache. If a node is returned, then the value of
* {@link #cacheSize} is decreased accordingly. The node that is returned
* will have <code>null</code> values for next, previous and element.
*
* @return A node, or <code>null</code> if there are no nodes in the cache.
*/
private Node getNodeFromCache() {
if (cacheSize == 0) {
return null;
}
Node cachedNode = firstCachedNode;
firstCachedNode = cachedNode.next;
cachedNode.next = null; // This should be changed anyway, but defensively
// set it to null.
cacheSize--;
return cachedNode;
}
private boolean cacheFull() {
return cacheSize >= maximumCacheSize;
}
/**
* 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.
*/
private void addNodeToCache(Node node) {
if (cacheFull()) {
// Don't cache the node.
return;
}
// Clear the node's contents and add it to the cache.
Node nextCachedNode = firstCachedNode;
node.previous = null;
node.next = nextCachedNode;
node.element = null;
firstCachedNode = node;
cacheSize++;
}
// Node operations
/**
* Create a node, getting it from the cache if possible.
*/
protected Node createNode() {
Node cachedNode = getNodeFromCache();
if (cachedNode == null) {
return super.createNode();
} else {
return cachedNode;
}
}
/**
* Create a node, getting it from the cache if possible.
*/
protected Node createNode(Node next, Node previous, Object element) {
Node cachedNode = getNodeFromCache();
if (cachedNode == null) {
return super.createNode(next, previous, element);
} else {
cachedNode.next = next;
cachedNode.previous = previous;
cachedNode.element = element;
return cachedNode;
}
}
/**
* Calls the superclass' implementation then calls
* {@link #addNodeToCache(Node)} on the node which has been removed.
*
* @see org.apache.commons.collections.CommonsLinkedList#removeNode(Node)
*/
protected void removeNode(Node node) {
super.removeNode(node);
addNodeToCache(node);
}
protected void removeAllNodes() {
// Add the removed nodes to the cache, then remove the rest.
// We can add them to the cache before removing them, since
// {@link CommonsLinkedList.removeAllNodes()} removes the
// nodes by removing references directly from {@link #marker}.
int numberOfNodesToCache = Math.min(size, maximumCacheSize - cacheSize);
Node node = marker.next;
for (int currentIndex = 0; currentIndex < numberOfNodesToCache; currentIndex++) {
Node oldNode = node;
node = node.next;
addNodeToCache(oldNode);
}
super.removeAllNodes();
}
}