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96 lines
3.2 KiB
Java
96 lines
3.2 KiB
Java
/*
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* Copyright (c) 2003, 2014, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package sun.swing;
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import java.util.*;
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/**
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* <b>WARNING:</b> This class is an implementation detail and is only
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* public so that it can be used by two packages. You should NOT consider
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* this public API.
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* <p>
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* <b>WARNING 2:</b> This is not a general purpose List implementation! It
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* has a specific use and will not work correctly if you use it outside of
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* its use.
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* <p>
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* A specialized ArrayList that caches its hashCode as well as overriding
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* equals to avoid creating an Iterator. This class is useful in scenarios
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* where the list won't change and you want to avoid the overhead of hashCode
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* iterating through the elements invoking hashCode. This also assumes you'll
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* only ever compare a BakedArrayList to another BakedArrayList.
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*
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* @author Scott Violet
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*/
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@SuppressWarnings("serial") // JDK-implementation class
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public class BakedArrayList<E> extends ArrayList<E> {
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/**
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* The cached hashCode.
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*/
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private int _hashCode;
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public BakedArrayList(int size) {
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super(size);
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}
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public BakedArrayList(java.util.List<? extends E> data) {
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this(data.size());
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for (int counter = 0, max = data.size(); counter < max; counter++){
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add(data.get(counter));
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}
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cacheHashCode();
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}
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/**
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* Caches the hash code. It is assumed you won't modify the list, or that
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* if you do you'll call cacheHashCode again.
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*/
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public void cacheHashCode() {
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_hashCode = 1;
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for (int counter = size() - 1; counter >= 0; counter--) {
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_hashCode = 31 * _hashCode + get(counter).hashCode();
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}
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}
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public int hashCode() {
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return _hashCode;
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}
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public boolean equals(Object o) {
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@SuppressWarnings("unchecked")
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BakedArrayList<E> list = (BakedArrayList)o;
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int size = size();
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if (list.size() != size) {
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return false;
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}
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while (size-- > 0) {
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if (!get(size).equals(list.get(size))) {
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return false;
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}
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}
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return true;
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}
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}
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