1 /*

     2  * Copyright 2003 Sun Microsystems, Inc.  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.  Sun designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

    22  * CA 95054 USA or visit www.sun.com if you need additional information or

    23  * have any 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 }