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1   /*
2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/util/StackedIterator.java,v 1.10 2005/01/30 03:14:41 elharo Exp $
3    * $Revision: 1.10 $
4    * $Date: 2005/01/30 03:14:41 $
5    *
6    * ====================================================================
7    *
8    * Copyright (C) 2000-2002 bob mcwhirter & James Strachan.
9    * All rights reserved.
10   *
11   * Redistribution and use in source and binary forms, with or without
12   * modification, are permitted provided that the following conditions
13   * are met:
14   * 
15   * 1. Redistributions of source code must retain the above copyright
16   *    notice, this list of conditions, and the following disclaimer.
17   *
18   * 2. Redistributions in binary form must reproduce the above copyright
19   *    notice, this list of conditions, and the disclaimer that follows 
20   *    these conditions in the documentation and/or other materials 
21   *    provided with the distribution.
22   *
23   * 3. The name "Jaxen" must not be used to endorse or promote products
24   *    derived from this software without prior written permission.  For
25   *    written permission, please contact license@jaxen.org.
26   * 
27   * 4. Products derived from this software may not be called "Jaxen", nor
28   *    may "Jaxen" appear in their name, without prior written permission
29   *    from the Jaxen Project Management (pm@jaxen.org).
30   * 
31   * In addition, we request (but do not require) that you include in the 
32   * end-user documentation provided with the redistribution and/or in the 
33   * software itself an acknowledgement equivalent to the following:
34   *     "This product includes software developed by the
35   *      Jaxen Project (http://www.jaxen.org/)."
36   * Alternatively, the acknowledgment may be graphical using the logos 
37   * available at http://www.jaxen.org/
38   *
39   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
40   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
41   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
42   * DISCLAIMED.  IN NO EVENT SHALL THE Jaxen AUTHORS OR THE PROJECT
43   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
44   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
45   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
46   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
47   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
48   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
49   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
50   * SUCH DAMAGE.
51   *
52   * ====================================================================
53   * This software consists of voluntary contributions made by many 
54   * individuals on behalf of the Jaxen Project and was originally 
55   * created by bob mcwhirter <bob@werken.com> and 
56   * James Strachan <jstrachan@apache.org>.  For more information on the 
57   * Jaxen Project, please see <http://www.jaxen.org/>.
58   * 
59   * $Id: StackedIterator.java,v 1.10 2005/01/30 03:14:41 elharo Exp $
60   */
61  
62  
63  
64  package org.jaxen.util;
65  
66  import java.util.HashSet;
67  import java.util.Iterator;
68  import java.util.LinkedList;
69  import java.util.NoSuchElementException;
70  import java.util.Set;
71  
72  import org.jaxen.Navigator;
73  
74  /***
75   * @deprecated this iterator is no longer used to implement any of the Jaxen axes. If you have implemented
76   * a navigator-specific axis based on this class, take a look at the DescendantAxisIterator for ideas 
77   * on how to remove that dependency.
78   */
79  public abstract class StackedIterator implements Iterator
80  {
81  
82      private LinkedList iteratorStack;
83      private Navigator  navigator;
84  
85      private Set        created;
86  
87      public StackedIterator(Object contextNode,
88                             Navigator navigator)
89      {
90          this.iteratorStack = new LinkedList();
91          this.created       = new HashSet();
92  
93          init( contextNode,
94                navigator );
95      }
96  
97      protected StackedIterator()
98      {
99          this.iteratorStack = new LinkedList();
100         this.created       = new HashSet();
101     }
102 
103     protected void init(Object contextNode,
104                         Navigator navigator)
105     {
106         this.navigator     = navigator;
107         
108         //pushIterator( internalCreateIterator( contextNode ) );
109     }
110 
111     protected Iterator internalCreateIterator(Object contextNode)
112     {
113         if ( this.created.contains( contextNode ) )
114         {
115             return null;
116         }
117 
118         this.created.add( contextNode );
119 
120         return createIterator( contextNode );
121     }
122 
123     public boolean hasNext()
124     {
125         Iterator curIter = currentIterator();
126 
127         if ( curIter == null )
128         {
129             return false;
130         }
131 
132         return curIter.hasNext();
133     }
134 
135     public Object next() throws NoSuchElementException
136     {
137         if ( ! hasNext() )
138         {
139             throw new NoSuchElementException();
140         }
141 
142         Iterator curIter = currentIterator();
143         Object   object  = curIter.next();
144 
145         pushIterator( internalCreateIterator( object ) );
146 
147         return object;
148     }
149 
150     public void remove() throws UnsupportedOperationException
151     {
152         throw new UnsupportedOperationException();
153     }
154 
155     abstract protected Iterator createIterator(Object contextNode);
156 
157     protected void pushIterator(Iterator iter)
158     {
159         if ( iter != null )
160         {
161             this.iteratorStack.addFirst(iter); //addLast( iter );
162         }
163     }
164 
165     private Iterator currentIterator()
166     {
167         while ( iteratorStack.size() > 0 )
168         {
169             Iterator curIter = (Iterator) iteratorStack.getFirst();
170 
171             if ( curIter.hasNext() )
172             {
173                 return curIter;
174             }
175 
176             iteratorStack.removeFirst();
177         }
178 
179         return null;
180     }
181 
182     protected Navigator getNavigator()
183     {
184         return this.navigator;
185     }
186 }