ArrayIterator


1   package org.apache.velocity.util;
2   
3   /*
4    * Copyright 1999-2001,2004 The Apache Software Foundation.
5    * 
6    * Licensed under the Apache License, Version 2.0 (the "License");
7    * you may not use this file except in compliance with the License.
8    * You may obtain a copy of the License at
9    * 
10   *      http://www.apache.org/licenses/LICENSE-2.0
11   * 
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  import java.util.Iterator  ;
20  import java.util.NoSuchElementException  ;
21  import java.lang.reflect.Array  ;
22  
23  
24  /**
25   *  <p>
26   *  An Iterator wrapper for an Object[]. This will
27   *  allow us to deal with all array like structures
28   *  in a consistent manner.
29   *  </p>
30   *  <p>
31   *  WARNING : this class's operations are NOT synchronized.
32   *  It is meant to be used in a single thread, newly created
33   *  for each use in the #foreach() directive.
34   *  If this is used or shared, synchronize in the
35   *  next() method.
36   *  </p>
37   *
38   * @author <a HREF="mailto:jvanzyl@apache.org">Jason van Zyl</a>
39   * @author <a HREF="mailto:geirm@apache.org">Geir Magnusson Jr.</a>
40   * @version $Id: ArrayIterator.java,v 1.6.8.1 2004/03/03 23:23:07 geirm Exp $
41   */
42  public class ArrayIterator implements Iterator  
43  {
44      /**
45       * The objects to iterate.
46       */
47      private Object   array;
48  
49      /**
50       * The current position and size in the array.
51       */
52      private int pos;
53      private int size;
54  
55      /**
56       * Creates a new iterator instance for the specified array.
57       *
58       * @param array The array for which an iterator is desired.
59       */
60      public ArrayIterator(Object   array)
61      {
62          /*
63           * if this isn't an array, then throw.  Note that this is 
64           * for internal use - so this should never happen - if it does
65           *  we screwed up.
66           */
67           
68          if ( !array.getClass().isArray() )
69          {   
70              throw new IllegalArgumentException  ( 
71                  "Programmer error : internal ArrayIterator invoked w/o array");
72          }
73              
74          this.array = array;
75          pos = 0;
76          size = Array.getLength( this.array );
77      }
78  
79      /**
80       * Move to next element in the array.
81       *
82       * @return The next object in the array.
83       */
84      public Object   next()
85      {
86          if (pos < size )
87              return Array.get( array, pos++);
88                  
89          /*
90           *  we screwed up...
91           */
92           
93          throw new NoSuchElementException  ("No more elements: " + pos +
94                                           " / " + size);
95      }
96      
97      /**
98       * Check to see if there is another element in the array.
99       *
100      * @return Whether there is another element.
101      */
102     public boolean hasNext()
103     {
104         return (pos < size );
105     }
106 
107     /**
108      * No op--merely added to satify the <code>Iterator</code> interface.
109      */
110     public void remove()
111     {
112         throw new UnsupportedOperationException  ();
113     }
114 }
115
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