ArrayIterator


1   /*
2    * Copyright 1999-2001,2004 The Apache Software Foundation.
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package org.apache.commons.jexl.util;
18  
19  
20  
21  import java.util.Iterator  ;
22  import java.util.NoSuchElementException  ;
23  import java.lang.reflect.Array  ;
24  
25  
26  /**
27   *  <p>
28   *  An Iterator wrapper for an Object[]. This will
29   *  allow us to deal with all array like structures
30   *  in a consistent manner.
31   *  </p>
32   *  <p>
33   *  WARNING : this class's operations are NOT synchronized.
34   *  It is meant to be used in a single thread, newly created
35   *  for each use in the #foreach() directive.
36   *  If this is used or shared, synchronize in the
37   *  next() method.
38   *  </p>
39   *
40   * @since 1.0
41   * @author <a HREF="mailto:jvanzyl@apache.org">Jason van Zyl</a>
42   * @author <a HREF="mailto:geirm@apache.org">Geir Magnusson Jr.</a>
43   * @version $Id: ArrayIterator.java 398329 2006-04-30 12:51:43Z dion $
44   */
45  public class ArrayIterator implements Iterator   {
46      /**
47       * The objects to iterate over.
48       */
49      private final Object   array;
50  
51      /**
52       * The current position and size in the array.
53       */
54      private int pos;
55  
56      /**
57       * The size of the array.
58       */
59      private final int size;
60  
61      /**
62       * Creates a new iterator instance for the specified array.
63       *
64       * @param arr The array for which an iterator is desired.
65       */
66      public ArrayIterator(Object   arr) {
67          /*
68           * if this isn't an array, then throw.  Note that this is 
69           * for internal use - so this should never happen - if it does
70           *  we screwed up.
71           */
72           
73          if (!arr.getClass().isArray()) {
74              throw new IllegalArgumentException  ("Programmer error :"
75                        + " internal ArrayIterator invoked w/o array");
76          }
77              
78          array = arr;
79          pos = 0;
80          size = Array.getLength(array);
81      }
82  
83      /**
84       * Move to next element in the array.
85       *
86       * @return The next object in the array.
87       */
88      public Object   next() {
89          if (pos < size) {
90              return Array.get(array, pos++);
91          }
92                  
93          /*
94           *  we screwed up...
95           */
96           
97          throw new NoSuchElementException  ("No more elements: " + pos
98                                           + " / " + size);
99      }
100     
101     /**
102      * Check to see if there is another element in the array.
103      *
104      * @return Whether there is another element.
105      */
106     public boolean hasNext() {
107         return (pos < size);
108     }
109 
110     /**
111      * No op--merely added to satify the <code>Iterator</code> interface.
112      */
113     public void remove() {
114         throw new UnsupportedOperationException  ();
115     }
116 }
117
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