1 /*
   2  * Copyright (c) 2003, 2014, 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 @SuppressWarnings("serial") // JDK-implementation class
  47 public class BakedArrayList extends ArrayList<Object> {
  48     /**
  49      * The cached hashCode.
  50      */
  51     private int _hashCode;
  52 
  53     public BakedArrayList(int size) {
  54         super(size);
  55     }
  56 
  57     public BakedArrayList(java.util.List<?> data) {
  58         this(data.size());
  59         for (int counter = 0, max = data.size(); counter < max; counter++){
  60             add(data.get(counter));
  61         }
  62         cacheHashCode();
  63     }
  64 
  65     /**
  66      * Caches the hash code. It is assumed you won't modify the list, or that
  67      * if you do you'll call cacheHashCode again.
  68      */
  69     public void cacheHashCode() {
  70         _hashCode = 1;
  71         for (int counter = size() - 1; counter >= 0; counter--) {
  72             _hashCode = 31 * _hashCode + get(counter).hashCode();
  73         }
  74     }
  75 
  76     public int hashCode() {
  77         return _hashCode;
  78     }
  79 
  80     public boolean equals(Object o) {
  81         BakedArrayList list = (BakedArrayList)o;
  82         int size = size();
  83 
  84         if (list.size() != size) {
  85             return false;
  86         }
  87         while (size-- > 0) {
  88             if (!get(size).equals(list.get(size))) {
  89                 return false;
  90             }
  91         }
  92         return true;
  93     }
  94 }