/*
* Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* questions.
*/
package com.sun.max.collect;
import com.sun.max.*;
/**
* Defines the semantics of key comparison in a {@linkplain HashMapping hash based data structure} where reference
* identity is used for {@linkplain #equivalent(Object, Object) equivalence} and the hash code are obtained from
* {@link System#identityHashCode(Object)}. There is a {@linkplain #instance(Class) singleton} instance of this class.
*/
public final class HashIdentity<T> implements HashEquivalence<T> {
private HashIdentity() {
}
public boolean equivalent(T object1, T object2) {
return object1 == object2;
}
public int hashCode(T object) {
if (object == null) {
return 0;
}
return System.identityHashCode(object);
}
private static final HashIdentity identity = new HashIdentity<Object>();
public static <T> HashIdentity<T> instance(Class<HashIdentity<T>> type) {
return Utils.cast(type, identity);
}
}