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comparison graal/com.oracle.max.base/src/com/sun/max/collect/HashEquality.java @ 3733:e233f5660da4

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Added Java files from Maxine project.
author Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
date Sat, 17 Dec 2011 19:59:18 +0100
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children bc8527f3071c
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3732:3e2e8b8abdaf 3733:e233f5660da4
1 /*
2 * Copyright (c) 2007, 2011, 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.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23 package com.sun.max.collect;
24
25 import com.sun.max.*;
26
27 /**
28 * Defines the semantics of key comparison in a {@linkplain HashMapping hash based data structure} that delegate to
29 * {@link Object#equals(Object)} and {@link Object#hashCode()}. There is a {@linkplain #instance(Class) singleton}
30 * instance of this class.
31 */
32 public final class HashEquality<T> implements HashEquivalence<T> {
33
34 private HashEquality() {
35 }
36
37 public boolean equivalent(T object1, T object2) {
38 if (object1 == null) {
39 return object2 == null;
40 }
41 return object1.equals(object2);
42 }
43
44 public int hashCode(T object) {
45 if (object == null) {
46 return 0;
47 }
48 return object.hashCode();
49 }
50
51 private static final HashEquality equality = new HashEquality<Object>();
52
53 public static <T> HashEquality<T> instance(Class<HashEquality<T>> type) {
54 return Utils.cast(type, equality);
55 }
56 }