nodelistimpl.java

用Java写的面相对象的数据库管理系统

/**
 * org/ozone-db/xml/dom/NodeListImpl.java
 *
 * The contents of this file are subject to the OpenXML Public
 * License Version 1.0; you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 * http://www.openxml.org/license.html
 *
 * THIS SOFTWARE IS DISTRIBUTED ON AN "AS IS" BASIS WITHOUT WARRANTY
 * OF ANY KIND, EITHER EXPRESSED OR IMPLIED. THE INITIAL DEVELOPER
 * AND ALL CONTRIBUTORS SHALL NOT BE LIABLE FOR ANY DAMAGES AS A
 * RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. SEE THE LICENSE FOR THE SPECIFIC LANGUAGE GOVERNING
 * RIGHTS AND LIMITATIONS UNDER THE LICENSE.
 *
 * The Initial Developer of this code under the License is Assaf Arkin.
 * Portions created by Assaf Arkin are Copyright (C) 1998, 1999.
 * All Rights Reserved.
 */

/**
 * Changes for Persistent DOM running with ozone are
 * Copyright 1999 by SMB GmbH. All rights reserved.
 */

package org.ozoneDB.xml.dom;

import org.w3c.dom.*;
import java.io.*;
import java.util.Vector;


/**
 * Used to traverse childs of a node. {@link org.w3c.dom.NodeList} is a live
 * list, meaning that any change to the node is reflected in this list and vice
 * versa.
 * <P>
 * The functionality of NodeList is implemented in {@link NodeImpl} itself
 * using a double-linked list. This class is only provided to hide the
 * interface of {@link NodeImpl}.
 * <P>
 * This class is not entirely thread-safe due to thread-safe limitations on
 * {@link NodeImpl} itself.
 *
 *
 * @version $Revision: 1.13 $ $Date: 2000/10/28 16:55:23 $
 * @author <a href="mailto:[e-mail]">Assaf Arkin</a>
 * @see NodeImpl
 */
public final class NodeListImpl implements NodeList, Serializable {
    
    final static long serialVersionUID = 1;
    
    
    /**
     * Return the nth child in the node (zero based). If the child does not exist,
     * returns null. No exception is thrown if index is negative.
     * @param index Index of child to return (zero based)
     * @return Child or null
     * @see NodeImpl#getChild
     */
    public Node item( int index ) {
        return index >= 0 && index < _nodes.size() ? (Node)_nodes.elementAt( index ) : null;
    } 
    
    
    /**
     * Return the number of childs in this node.
     * @return Number of childs
     */
    public int getLength() {
        return _nodes.size();
    } 
    
    
    /**
     * Constructor requires node.
     * @param node Node to traverse
     */
    public NodeListImpl( Node node ) {
        if (node == null) {
            throw new NullPointerException( "Argument 'node' is null." );
        } 
        
        _rootNode = node;
        _nodes = new Vector();
        
        Node child = node.getFirstChild();
        while (child != null) {
            _nodes.addElement( child );
            child = child.getNextSibling();
        } 
    }
    
    /**
     * The node which this list traverses.
     */
    protected Node _rootNode;
    protected Vector _nodes;
    
}