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1   package org.apache.maven.shared.dependency.tree;
2   
3   /*
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *   http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing,
15   * software distributed under the License is distributed on an
16   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17   * KIND, either express or implied.  See the License for the
18   * specific language governing permissions and limitations
19   * under the License.
20   */
21  
22  import java.util.Iterator;
23  import java.util.List;
24  import java.util.NoSuchElementException;
25  import java.util.Stack;
26  
27  /**
28   * {@link Iterator} for {@link DependencyNode} implementing a preoder traversal.
29   * 
30   * @author <a href="mailto:carlos@apache.org">Carlos Sanchez</a>
31   * @version $Id: DependencyTreePreorderIterator.java 661727 2008-05-30 14:21:49Z bentmann $
32   */
33  public class DependencyTreePreorderIterator
34      implements Iterator
35  {
36      private Stack nodesToProcess = new Stack();
37  
38      public DependencyTreePreorderIterator( DependencyNode rootNode )
39      {
40          nodesToProcess.push( rootNode );
41      }
42  
43      public boolean hasNext()
44      {
45          return !nodesToProcess.isEmpty();
46      }
47  
48      public Object next()
49      {
50          if ( !hasNext() )
51          {
52              throw new NoSuchElementException();
53          }
54          DependencyNode currentNode = (DependencyNode) nodesToProcess.pop();
55          List children = currentNode.getChildren();
56          if ( children != null )
57          {
58              for ( int i = children.size() - 1; i >= 0; i-- )
59              {
60                  nodesToProcess.push( children.get( i ) );
61              }
62          }
63          return currentNode;
64      }
65  
66      /**
67       * @throws UnsupportedOperationException
68       */
69      public void remove()
70      {
71          throw new UnsupportedOperationException();
72      }
73  }