Performance optimised LinkedList, from Jeff Varszegi
git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/collections/trunk@130866 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Stephen Colebourne
parent
7510ff1b6d
commit
4fbfa16c6e
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@ -0,0 +1,876 @@
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/*
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* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/java/org/apache/commons/collections/Attic/NodeCachingLinkedList.java,v 1.1 2002/11/18 23:58:17 scolebourne Exp $
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* $Revision: 1.1 $
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* $Date: 2002/11/18 23:58:17 $
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*
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* ====================================================================
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*
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* The Apache Software License, Version 1.1
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*
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* Copyright (c) 1999-2002 The Apache Software Foundation. All rights
|
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* reserved.
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*
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* Redistribution and use in source and binary forms, with or without
|
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* modification, are permitted provided that the following conditions
|
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
|
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* notice, this list of conditions and the following disclaimer.
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*
|
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* 2. Redistributions in binary form must reproduce the above copyright
|
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* notice, this list of conditions and the following disclaimer in
|
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* the documentation and/or other materials provided with the
|
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* distribution.
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*
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* 3. The end-user documentation included with the redistribution, if
|
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* any, must include the following acknowlegement:
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* "This product includes software developed by the
|
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* Apache Software Foundation (http://www.apache.org/)."
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* Alternately, this acknowlegement may appear in the software itself,
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* if and wherever such third-party acknowlegements normally appear.
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*
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* 4. The names "The Jakarta Project", "Commons", and "Apache Software
|
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* Foundation" must not be used to endorse or promote products derived
|
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* from this software without prior written permission. For written
|
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* permission, please contact apache@apache.org.
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*
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* 5. Products derived from this software may not be called "Apache"
|
||||
* nor may "Apache" appear in their names without prior written
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||||
* permission of the Apache Group.
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*
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* 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
|
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* 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
|
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
||||
* SUCH DAMAGE.
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* ====================================================================
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*
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* This software consists of voluntary contributions made by many
|
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* individuals on behalf of the Apache Software Foundation. For more
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* information on the Apache Software Foundation, please see
|
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* <http://www.apache.org/>.
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*
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*/
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package org.apache.commons.collections;
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import java.io.Serializable;
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import java.util.Collection;
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import java.util.ConcurrentModificationException;
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import java.util.Iterator;
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import java.util.LinkedList;
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import java.util.List;
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import java.util.ListIterator;
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import java.util.NoSuchElementException;
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/**
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* <code>NodeCachingLinkedList</code> is a linked list implementation that
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* provides better performance than java.util.LinkedList.
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* <p>
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* This class differs from java.util.LinkedList in that internal Node
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* objects used to hold the elements are not necessarily thrown away when an
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* entry is removed from the list. Instead, they are cached, which allows this
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* implementation to give better performance than java.util.LinkedList with a
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* small space penalty.
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* <p>
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* <b>Note that this implementation is not synchronized.</b> If multiple
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* threads access a list concurrently, and at least one of the threads
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* modifies the list structurally, it <i>must</i> be synchronized
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* externally.
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* <p>
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* The iterators returned by the this class's <code>iterator</code> and
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* <code>listIterator</code> methods are <i>fail-fast</i>: if the list is
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* structurally modified at any time after the iterator is created, in any way
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* except through the Iterator's own <code>remove</code> or <code>add</code> methods,
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* the iterator will throw a <code>ConcurrentModificationException</code>. Thus,
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* in the face of concurrent modification, the iterator fails quickly and
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* cleanly, rather than risking arbitrary, non-deterministic behavior at an
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* undetermined time in the future.
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* <p>
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* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
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* as it is, generally speaking, impossible to make any hard guarantees in the
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* presence of unsynchronized concurrent modification. Fail-fast iterators
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* throw <code>ConcurrentModificationException</code> on a best-effort basis.
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* Therefore, it would be wrong to write a program that depended on this
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* exception for its correctness: <i>the fail-fast behavior of iterators
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* should be used only to detect bugs.</i>
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*
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* @author Jeff Varszegi
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*/
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public final class NodeCachingLinkedList
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extends LinkedList
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implements List, Cloneable, Serializable {
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private static final int MINIMUM_MAXIMUM_CACHE_SIZE = 100;
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private static final int DEFAULT_MAXIMUM_CACHE_SIZE = 1000000;
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private Node cacheHeader = new Node(null, null, null);
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private int cacheCount = 0;
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private int maximumCacheSize = DEFAULT_MAXIMUM_CACHE_SIZE;
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private Node header = new Node(null, null, null);
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private int size = 0;
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/**
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* Constructs an empty list.
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*/
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public NodeCachingLinkedList() {
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header.next = header.previous = header;
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}
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/**
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* Constructs a list containing the elements of the specified
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* collection, in the order they are returned by the collection's
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* iterator.
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*
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* @param coll the collection whose elements are to be placed into this list.
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* @throws NullPointerException if the specified collection is null.
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*/
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public NodeCachingLinkedList(Collection coll) {
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this();
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addAll(coll);
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}
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/**
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* Sets the maximum number of elements that may be held in the internal
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* reusable node cache.
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*
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* @return the maximum cache size
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*/
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public int getMaximumCacheSize() {
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return maximumCacheSize;
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}
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/**
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* Sets the maximum number of elements that may be held in the internal
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* reusable node cache.
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*
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* @param maximumCacheSize the maximum cache size to set
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*/
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public void setMaximumCacheSize(int maximumCacheSize) {
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this.maximumCacheSize = maximumCacheSize;
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}
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/**
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* Returns the first element in this list.
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*
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* @return the first object in the list
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* @throws NoSuchElementException if this list is empty
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*/
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public Object getFirst() {
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if (size == 0) {
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throw new NoSuchElementException();
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}
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else {
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return header.next.element;
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}
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}
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/**
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* Returns the last element in this list.
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*
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* @return the last object in the list
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* @throws NoSuchElementException if this list is empty
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*/
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public Object getLast() {
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if (size == 0) {
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throw new NoSuchElementException();
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}
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return header.previous.element;
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}
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/**
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* Removes and returns the first element from this list.
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*
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* @return the first element from this list, now removed
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* @throws NoSuchElementException if this list is empty
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*/
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public Object removeFirst() {
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if (size == 0) {
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throw new NoSuchElementException();
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}
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Node firstNode = header.next;
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Object first = firstNode.element;
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firstNode.next.previous = header;
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header.next = firstNode.next;
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size--;
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modCount++;
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if (cacheCount < maximumCacheSize) {
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firstNode.element = null;
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firstNode.next = cacheHeader.next;
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cacheHeader.next = firstNode;
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cacheCount++;
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}
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return first;
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}
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/**
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* Removes and returns the last element from this list.
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*
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* @return the last element from this list, now removed
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* @throws NoSuchElementException if this list is empty
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*/
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public Object removeLast() {
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if (size == 0) {
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throw new NoSuchElementException();
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}
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Node lastNode = header.previous;
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Object last = lastNode.element;
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lastNode.previous.next = header;
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header.previous = lastNode.previous;
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size--;
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modCount++;
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if (cacheCount < maximumCacheSize) {
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lastNode.element = null;
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lastNode.previous = null;
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lastNode.next = cacheHeader.next;
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cacheHeader.next = lastNode;
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cacheCount++;
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}
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return last;
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}
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/**
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* Inserts the given element at the beginning of this list.
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*
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* @param obj the element to be inserted at the beginning of this list
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*/
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public void addFirst(Object obj) {
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Node newNode;
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if (cacheCount > 0) {
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newNode = cacheHeader.next;
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cacheHeader.next = newNode.next;
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newNode.element = obj;
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newNode.next = header.next;
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newNode.previous = header;
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cacheCount--;
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}
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else {
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newNode = new Node(obj, header.next, header);
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}
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newNode.previous.next = newNode;
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newNode.next.previous = newNode;
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size++;
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modCount++;
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}
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/**
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* Appends the given element to the end of this list. (Identical in
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* function to the <code>add</code> method; included only for consistency.)
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*
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* @param obj the element to be inserted at the end of this list
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*/
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public void addLast(Object obj) {
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Node newNode;
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if (cacheCount > 0) {
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newNode = cacheHeader.next;
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cacheHeader.next = newNode.next;
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newNode.element = obj;
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newNode.next = header.next;
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newNode.previous = header;
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cacheCount--;
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}
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else {
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newNode = new Node(obj, header, header.previous);
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}
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newNode.previous.next = newNode;
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newNode.next.previous = newNode;
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size++;
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modCount++;
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}
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/**
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* Returns <code>true</code> if this list contains the specified element.
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* More formally, returns <code>true</code> if and only if this list contains
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* at least one element <code>e</code> such that <code>(o==null ? e==null
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* : o.equals(e))</code>.
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*
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* @param obj element whose presence in this list is to be tested
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* @return <code>true</code> if this list contains the specified element
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*/
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public boolean contains(Object obj) {
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return indexOf(obj) != -1;
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}
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/**
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* Returns the number of elements in this list.
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*
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* @return the number of elements in this list
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*/
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public int size() {
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return size;
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}
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/**
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* Appends the specified element to the end of this list.
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*
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* @param obj element to be appended to this list.
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* @return <code>true</code> (as per the general contract of
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* <code>Collection.add</code>)
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*/
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public boolean add(Object obj) {
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addLast(obj);
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return true;
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}
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/**
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* Removes the first occurrence of the specified element in this list. If
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* the list does not contain the element, it is unchanged. More formally,
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* removes the element with the lowest index <code>i</code> such that
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* <code>(o==null ? get(i)==null : o.equals(get(i)))</code> (if such an
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* element exists).
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*
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* @param obj element to be removed from this list, if present
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* @return <code>true</code> if the list contained the specified element
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*/
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public boolean remove(Object obj) {
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if (obj == null) {
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for (Node e = header.next; e != header; e = e.next) {
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if (e.element == null) {
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remove(e);
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return true;
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}
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}
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}
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else {
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for (Node e = header.next; e != header; e = e.next) {
|
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if (obj.equals(e.element)) {
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remove(e);
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return true;
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}
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}
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}
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return false;
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}
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/**
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* Appends all of the elements in the specified collection to the end of
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* this list, in the order that they are returned by the specified
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* collection's iterator. The behavior of this operation is undefined if
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* the specified collection is modified while the operation is in
|
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* progress. (This implies that the behavior of this call is undefined if
|
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* the specified Collection is this list, and this list is nonempty.)
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*
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* @param coll the elements to be inserted into this list
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* @return <code>true</code> if this list changed as a result of the call
|
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* @throws NullPointerException if the specified collection is null
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*/
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public boolean addAll(Collection coll) {
|
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return addAll(size, coll);
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}
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|
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/**
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* Inserts all of the elements in the specified collection into this
|
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* list, starting at the specified position. Shifts the element
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* currently at that position (if any) and any subsequent elements to
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* the right (increases their indices). The new elements will appear
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* in the list in the order that they are returned by the
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* specified collection's iterator.
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*
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* @param index index at which to insert first element
|
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* from the specified collection
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* @param coll elements to be inserted into this list
|
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* @return <code>true</code> if this list changed as a result of the call
|
||||
* @throws IndexOutOfBoundsException if the specified index is out of
|
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* range (<code>index < 0 || index > size()</code>)
|
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* @throws NullPointerException if the specified collection is null
|
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*/
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public boolean addAll(int index, Collection coll) {
|
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int numNew = coll.size();
|
||||
if (numNew == 0)
|
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return false;
|
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modCount++;
|
||||
|
||||
Node successor = (index == size ? header : entry(index));
|
||||
Node predecessor = successor.previous;
|
||||
Iterator it = coll.iterator();
|
||||
for (int i = 0; i < numNew; i++) {
|
||||
Node e;
|
||||
if (cacheCount > 0) {
|
||||
e = cacheHeader.next;
|
||||
cacheHeader.next = e.next;
|
||||
e.element = it.next();
|
||||
e.next = successor;
|
||||
e.previous = predecessor;
|
||||
}
|
||||
else {
|
||||
e = new Node(it.next(), successor, predecessor);
|
||||
}
|
||||
|
||||
predecessor.next = e;
|
||||
predecessor = e;
|
||||
}
|
||||
successor.previous = predecessor;
|
||||
|
||||
size += numNew;
|
||||
return true;
|
||||
}
|
||||
|
||||
/**
|
||||
* Removes all of the elements from this list.
|
||||
*/
|
||||
public void clear() {
|
||||
modCount++;
|
||||
header.next = header.previous = header;
|
||||
size = 0;
|
||||
}
|
||||
|
||||
// Positional Access Operations
|
||||
|
||||
/**
|
||||
* Returns the element at the specified position in this list.
|
||||
*
|
||||
* @param index index of element to return
|
||||
* @return the element at the specified position in this list
|
||||
*
|
||||
* @throws IndexOutOfBoundsException if the specified index is is out of
|
||||
* range (<code>index < 0 || index >= size()</code>)
|
||||
*/
|
||||
public Object get(int index) {
|
||||
if (index < 0 || index >= size) {
|
||||
throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);
|
||||
}
|
||||
Node e = header;
|
||||
if (index < (size >> 1)) {
|
||||
for (int i = 0; i <= index; i++) {
|
||||
e = e.next;
|
||||
}
|
||||
}
|
||||
else {
|
||||
for (int i = size; i > index; i--) {
|
||||
e = e.previous;
|
||||
}
|
||||
}
|
||||
return e.element;
|
||||
}
|
||||
|
||||
/**
|
||||
* Replaces the element at the specified position in this list with the
|
||||
* specified element.
|
||||
*
|
||||
* @param index index of element to replace
|
||||
* @param element element to be stored at the specified position
|
||||
* @return the element previously at the specified position
|
||||
* @throws IndexOutOfBoundsException if the specified index is out of
|
||||
* range (<code>index < 0 || index >= size()</code>)
|
||||
*/
|
||||
public Object set(int index, Object element) {
|
||||
Node e = entry(index);
|
||||
Object oldVal = e.element;
|
||||
e.element = element;
|
||||
return oldVal;
|
||||
}
|
||||
|
||||
/**
|
||||
* Inserts the specified element at the specified position in this list.
|
||||
* Shifts the element currently at that position (if any) and any
|
||||
* subsequent elements to the right (adds one to their indices).
|
||||
*
|
||||
* @param index index at which the specified element is to be inserted
|
||||
* @param element element to be inserted
|
||||
*
|
||||
* @throws IndexOutOfBoundsException if the specified index is out of
|
||||
* range (<code>index < 0 || index > size()</code>)
|
||||
*/
|
||||
public void add(int index, Object element) {
|
||||
Node e = (index == size ? header : entry(index));
|
||||
Node newNode;
|
||||
if (cacheCount > 0) {
|
||||
newNode = cacheHeader.next;
|
||||
cacheHeader.next = newNode.next;
|
||||
newNode.element = element;
|
||||
newNode.next = e;
|
||||
newNode.previous = e.previous;
|
||||
}
|
||||
else {
|
||||
newNode = new Node(element, e, e.previous);
|
||||
}
|
||||
|
||||
newNode.previous.next = newNode;
|
||||
newNode.next.previous = newNode;
|
||||
size++;
|
||||
modCount++;
|
||||
}
|
||||
|
||||
/**
|
||||
* Removes the element at the specified position in this list. Shifts any
|
||||
* subsequent elements to the left (subtracts one from their indices).
|
||||
* Returns the element that was removed from the list.
|
||||
*
|
||||
* @param index the index of the element to removed
|
||||
* @return the element previously at the specified position
|
||||
*
|
||||
* @throws IndexOutOfBoundsException if the specified index is out of
|
||||
* range (<code>index < 0 || index >= size()</code>)
|
||||
*/
|
||||
public Object remove(int index) {
|
||||
Node e = entry(index);
|
||||
Object data = e.element;
|
||||
remove(e);
|
||||
return data;
|
||||
}
|
||||
|
||||
/**
|
||||
* Return the indexed entry.
|
||||
*/
|
||||
private Node entry(int index) {
|
||||
if (index < 0 || index >= size) {
|
||||
throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);
|
||||
}
|
||||
Node e = header;
|
||||
if (index < (size >> 1)) {
|
||||
for (int i = 0; i <= index; i++) {
|
||||
e = e.next;
|
||||
}
|
||||
}
|
||||
else {
|
||||
for (int i = size; i > index; i--) {
|
||||
e = e.previous;
|
||||
}
|
||||
}
|
||||
return e;
|
||||
}
|
||||
|
||||
// Search Operations
|
||||
|
||||
/**
|
||||
* Returns the index in this list of the first occurrence of the
|
||||
* specified element, or -1 if the List does not contain this
|
||||
* element. More formally, returns the lowest index i such that
|
||||
* <code>(o==null ? get(i)==null : o.equals(get(i)))</code>, or -1 if
|
||||
* there is no such index.
|
||||
*
|
||||
* @param obj element to search for
|
||||
* @return the index in this list of the first occurrence of the
|
||||
* specified element, or -1 if the list does not contain this
|
||||
* element
|
||||
*/
|
||||
public int indexOf(Object obj) {
|
||||
int index = 0;
|
||||
if (obj == null) {
|
||||
for (Node e = header.next; e != header; e = e.next) {
|
||||
if (e.element == null)
|
||||
return index;
|
||||
index++;
|
||||
}
|
||||
}
|
||||
else {
|
||||
for (Node e = header.next; e != header; e = e.next) {
|
||||
if (obj.equals(e.element))
|
||||
return index;
|
||||
index++;
|
||||
}
|
||||
}
|
||||
return -1;
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns the index in this list of the last occurrence of the
|
||||
* specified element, or -1 if the list does not contain this
|
||||
* element. More formally, returns the highest index i such that
|
||||
* <code>(o==null ? get(i)==null : o.equals(get(i)))</code>, or -1 if
|
||||
* there is no such index.
|
||||
*
|
||||
* @param obj element to search for
|
||||
* @return the index in this list of the last occurrence of the
|
||||
* specified element, or -1 if the list does not contain this
|
||||
* element
|
||||
*/
|
||||
public int lastIndexOf(Object obj) {
|
||||
int index = size;
|
||||
if (obj == null) {
|
||||
for (Node e = header.previous; e != header; e = e.previous) {
|
||||
index--;
|
||||
if (e.element == null)
|
||||
return index;
|
||||
}
|
||||
}
|
||||
else {
|
||||
for (Node e = header.previous; e != header; e = e.previous) {
|
||||
index--;
|
||||
if (obj.equals(e.element))
|
||||
return index;
|
||||
}
|
||||
}
|
||||
return -1;
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns a list-iterator of the elements in this list (in proper
|
||||
* sequence), starting at the specified position in the list.
|
||||
* Obeys the general contract of <code>List.listIterator(int)</code>.<p>
|
||||
* <p>
|
||||
* The list-iterator is <i>fail-fast</i>: if the list is structurally
|
||||
* modified at any time after the Iterator is created, in any way except
|
||||
* through the list-iterator's own <code>remove</code> or <code>add</code>
|
||||
* methods, the list-iterator will throw a
|
||||
* <code>ConcurrentModificationException</code>. Thus, in the face of
|
||||
* concurrent modification, the iterator fails quickly and cleanly, rather
|
||||
* than risking arbitrary, non-deterministic behavior at an undetermined
|
||||
* time in the future.
|
||||
*
|
||||
* @param index index of first element to be returned from the
|
||||
* list-iterator (by a call to <code>next</code>)
|
||||
* @return a ListIterator of the elements in this list (in proper
|
||||
* sequence), starting at the specified position in the list
|
||||
* @throws IndexOutOfBoundsException if index is out of range
|
||||
* (<code>index < 0 || index > size()</code>)
|
||||
* @see List#listIterator(int)
|
||||
*/
|
||||
public ListIterator listIterator(int index) {
|
||||
return new ListItr(index);
|
||||
}
|
||||
|
||||
private final class ListItr implements ListIterator {
|
||||
private Node lastReturned = header;
|
||||
private Node next;
|
||||
private int nextIndex;
|
||||
private int expectedModCount = modCount;
|
||||
|
||||
ListItr(int index) {
|
||||
if (index < 0 || index > size)
|
||||
throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);
|
||||
if (index < (size >> 1)) {
|
||||
next = header.next;
|
||||
for (nextIndex = 0; nextIndex < index; nextIndex++)
|
||||
next = next.next;
|
||||
}
|
||||
else {
|
||||
next = header;
|
||||
for (nextIndex = size; nextIndex > index; nextIndex--)
|
||||
next = next.previous;
|
||||
}
|
||||
}
|
||||
|
||||
public boolean hasNext() {
|
||||
return nextIndex != size;
|
||||
}
|
||||
|
||||
public Object next() {
|
||||
checkForComodification();
|
||||
if (nextIndex == size)
|
||||
throw new NoSuchElementException();
|
||||
|
||||
lastReturned = next;
|
||||
next = next.next;
|
||||
nextIndex++;
|
||||
return lastReturned.element;
|
||||
}
|
||||
|
||||
public boolean hasPrevious() {
|
||||
return nextIndex != 0;
|
||||
}
|
||||
|
||||
public Object previous() {
|
||||
if (nextIndex == 0)
|
||||
throw new NoSuchElementException();
|
||||
|
||||
lastReturned = next = next.previous;
|
||||
nextIndex--;
|
||||
checkForComodification();
|
||||
return lastReturned.element;
|
||||
}
|
||||
|
||||
public int nextIndex() {
|
||||
return nextIndex;
|
||||
}
|
||||
|
||||
public int previousIndex() {
|
||||
return nextIndex - 1;
|
||||
}
|
||||
|
||||
public void remove() {
|
||||
checkForComodification();
|
||||
try {
|
||||
NodeCachingLinkedList.this.remove(lastReturned);
|
||||
}
|
||||
catch (NoSuchElementException e) {
|
||||
throw new IllegalStateException();
|
||||
}
|
||||
if (next == lastReturned)
|
||||
next = lastReturned.next;
|
||||
else
|
||||
nextIndex--;
|
||||
lastReturned = header;
|
||||
expectedModCount++;
|
||||
}
|
||||
|
||||
public void set(Object o) {
|
||||
if (lastReturned == header)
|
||||
throw new IllegalStateException();
|
||||
checkForComodification();
|
||||
lastReturned.element = o;
|
||||
}
|
||||
|
||||
public void add(Object o) {
|
||||
checkForComodification();
|
||||
lastReturned = header;
|
||||
|
||||
Node newNode;
|
||||
if (cacheCount > 0) {
|
||||
newNode = cacheHeader.next;
|
||||
cacheHeader.next = newNode.next;
|
||||
newNode.element = o;
|
||||
newNode.next = next;
|
||||
newNode.previous = next.previous;
|
||||
}
|
||||
else {
|
||||
newNode = new Node(o, next, next.previous);
|
||||
}
|
||||
|
||||
newNode.previous.next = newNode;
|
||||
newNode.next.previous = newNode;
|
||||
size++;
|
||||
modCount++;
|
||||
|
||||
nextIndex++;
|
||||
expectedModCount++;
|
||||
}
|
||||
|
||||
private void checkForComodification() {
|
||||
if (modCount != expectedModCount)
|
||||
throw new ConcurrentModificationException();
|
||||
}
|
||||
}
|
||||
|
||||
private final static class Node implements Serializable {
|
||||
Object element;
|
||||
Node next;
|
||||
Node previous;
|
||||
|
||||
Node(Object element, Node next, Node previous) {
|
||||
this.element = element;
|
||||
this.next = next;
|
||||
this.previous = previous;
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
private Node addsBefore(Object o, Node e) {
|
||||
Node newNode;
|
||||
if (cacheCount > 0) {
|
||||
newNode = cacheHeader.next;
|
||||
cacheHeader.next = newNode.next;
|
||||
newNode.element = o;
|
||||
newNode.next = e;
|
||||
newNode.previous = e.previous;
|
||||
}
|
||||
else {
|
||||
newNode = new Node(o, e, e.previous);
|
||||
}
|
||||
|
||||
newNode.previous.next = newNode;
|
||||
newNode.next.previous = newNode;
|
||||
size++;
|
||||
modCount++;
|
||||
return newNode;
|
||||
}
|
||||
|
||||
|
||||
private void remove(Node e) {
|
||||
if (e == header) {
|
||||
throw new NoSuchElementException();
|
||||
}
|
||||
e.previous.next = e.next;
|
||||
e.next.previous = e.previous;
|
||||
size--;
|
||||
modCount++;
|
||||
|
||||
if (cacheCount < maximumCacheSize) {
|
||||
e.element = null;
|
||||
e.previous = null;
|
||||
e.next = cacheHeader.next;
|
||||
cacheHeader.next = e;
|
||||
cacheCount++;
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns a shallow copy of this <code>NodeCachingLinkedList</code>. (The elements
|
||||
* themselves are not cloned.)
|
||||
*
|
||||
* @return a shallow copy of this <code>NodeCachingLinkedList</code> instance
|
||||
*/
|
||||
public Object clone() {
|
||||
NodeCachingLinkedList clone = new NodeCachingLinkedList();
|
||||
clone.setMaximumCacheSize(maximumCacheSize);
|
||||
|
||||
// Initialize clone with our elements
|
||||
for (Node e = header.next; e != header; e = e.next) {
|
||||
clone.add(e.element);
|
||||
}
|
||||
|
||||
return clone;
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns an array containing all of the elements in this list
|
||||
* in the correct order.
|
||||
*
|
||||
* @return an array containing all of the elements in this list
|
||||
* in the correct order
|
||||
*/
|
||||
public Object[] toArray() {
|
||||
Object[] result = new Object[size];
|
||||
int i = 0;
|
||||
for (Node e = header.next; e != header; e = e.next)
|
||||
result[i++] = e.element;
|
||||
return result;
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns an array containing all of the elements in this list in
|
||||
* the correct order; the runtime type of the returned array is that of
|
||||
* the specified array. If the list fits in the specified array, it
|
||||
* is returned therein. Otherwise, a new array is allocated with the
|
||||
* runtime type of the specified array and the size of this list.<p>
|
||||
* <p>
|
||||
* If the list fits in the specified array with room to spare
|
||||
* (i.e., the array has more elements than the list),
|
||||
* the element in the array immediately following the end of the
|
||||
* collection is set to null. This is useful in determining the length
|
||||
* of the list <i>only</i> if the caller knows that the list
|
||||
* does not contain any null elements.
|
||||
*
|
||||
* @param a the array into which the elements of the list are to
|
||||
* be stored, if it is big enough; otherwise, a new array of the
|
||||
* same runtime type is allocated for this purpose
|
||||
* @return an array containing the elements of the list
|
||||
* @throws ArrayStoreException if the runtime type of a is not a
|
||||
* supertype of the runtime type of every element in this list
|
||||
* @throws NullPointerException if the specified array is null
|
||||
*/
|
||||
public Object[] toArray(Object a[]) {
|
||||
if (a.length < size)
|
||||
a = (Object[]) java.lang.reflect.Array.newInstance(a.getClass().getComponentType(), size);
|
||||
int i = 0;
|
||||
for (Node e = header.next; e != header; e = e.next)
|
||||
a[i++] = e.element;
|
||||
|
||||
if (a.length > size)
|
||||
a[size] = null;
|
||||
|
||||
return a;
|
||||
}
|
||||
|
||||
}
|
||||
Loading…
Reference in New Issue