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 }