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1   /*
2    * Copyright (c) 2003, Oracle and/or its affiliates. All rights reserved.
3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4    *
5    * This code is free software; you can redistribute it and/or modify it
6    * under the terms of the GNU General Public License version 2 only, as
7    * published by the Free Software Foundation.  Oracle designates this
8    * particular file as subject to the "Classpath" exception as provided
9    * by Oracle in the LICENSE file that accompanied this code.
10   *
11   * This code is distributed in the hope that it will be useful, but WITHOUT
12   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14   * version 2 for more details (a copy is included in the LICENSE file that
15   * accompanied this code).
16   *
17   * You should have received a copy of the GNU General Public License version
18   * 2 along with this work; if not, write to the Free Software Foundation,
19   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20   *
21   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22   * or visit www.oracle.com if you need additional information or have any
23   * questions.
24   */
25  package sun.swing;
26  
27  import java.util.*;
28  
29  /**
30   * <b>WARNING:</b> This class is an implementation detail and is only
31   * public so that it can be used by two packages. You should NOT consider
32   * this public API.
33   * <p>
34   * <b>WARNING 2:</b> This is not a general purpose List implementation! It
35   * has a specific use and will not work correctly if you use it outside of
36   * its use.
37   * <p>
38   * A specialized ArrayList that caches its hashCode as well as overriding
39   * equals to avoid creating an Iterator. This class is useful in scenarios
40   * where the list won't change and you want to avoid the overhead of hashCode
41   * iterating through the elements invoking hashCode. This also assumes you'll
42   * only ever compare a BakedArrayList to another BakedArrayList.
43   *
44   * @author Scott Violet
45   */
46  public class BakedArrayList extends ArrayList {
47      /**
48       * The cached hashCode.
49       */
50      private int _hashCode;
51  
52      public BakedArrayList(int size) {
53          super(size);
54      }
55  
56      public BakedArrayList(java.util.List data) {
57          this(data.size());
58          for (int counter = 0, max = data.size(); counter < max; counter++){
59              add(data.get(counter));
60          }
61          cacheHashCode();
62      }
63  
64      /**
65       * Caches the hash code. It is assumed you won't modify the list, or that
66       * if you do you'll call cacheHashCode again.
67       */
68      public void cacheHashCode() {
69          _hashCode = 1;
70          for (int counter = size() - 1; counter >= 0; counter--) {
71              _hashCode = 31 * _hashCode + get(counter).hashCode();
72          }
73      }
74  
75      public int hashCode() {
76          return _hashCode;
77      }
78  
79      public boolean equals(Object o) {
80          BakedArrayList list = (BakedArrayList)o;
81          int size = size();
82  
83          if (list.size() != size) {
84              return false;
85          }
86          while (size-- > 0) {
87              if (!get(size).equals(list.get(size))) {
88                  return false;
89              }
90          }
91          return true;
92      }
93  }