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annotate graal/com.oracle.max.base/src/com/sun/max/collect/HashIdentity.java @ 4142:bc8527f3071c

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Adjust code base to new level of warnings.
author Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
date Sun, 18 Dec 2011 05:24:06 +0100
parents e233f5660da4
children
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1 /*
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2 * Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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20 * or visit www.oracle.com if you need additional information or have any
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21 * questions.
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22 */
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23 package com.sun.max.collect;
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25 import com.sun.max.*;
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27 /**
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28 * Defines the semantics of key comparison in a {@linkplain HashMapping hash based data structure} where reference
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29 * identity is used for {@linkplain #equivalent(Object, Object) equivalence} and the hash code are obtained from
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30 * {@link System#identityHashCode(Object)}. There is a {@linkplain #instance(Class) singleton} instance of this class.
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31 */
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32 public final class HashIdentity<T> implements HashEquivalence<T> {
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34 private HashIdentity() {
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35 }
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36
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37 public boolean equivalent(T object1, T object2) {
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38 return object1 == object2;
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39 }
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41 public int hashCode(T object) {
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42 if (object == null) {
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43 return 0;
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44 }
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45 return System.identityHashCode(object);
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46 }
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47
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48 private static final HashIdentity identity = new HashIdentity<>();
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49
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50 public static <T> HashIdentity<T> instance(Class<HashIdentity<T>> type) {
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51 return Utils.cast(type, identity);
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52 }
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53 }