110 lines
3.2 KiB
Java
110 lines
3.2 KiB
Java
//******************************************************************************
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//
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// File: IdentityPair.java
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// Package: edu.rit.util
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// Unit: Class edu.rit.util.IdentityPair
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//
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// This Java source file is copyright (C) 2015 by Alan Kaminsky. All rights
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// reserved. For further information, contact the author, Alan Kaminsky, at
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// ark@cs.rit.edu.
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//
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// This Java source file is part of the Parallel Java 2 Library ("PJ2"). PJ2 is
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// free software; you can redistribute it and/or modify it under the terms of
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// the GNU General Public License as published by the Free Software Foundation;
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// either version 3 of the License, or (at your option) any later version.
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//
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// PJ2 is distributed in the hope that it will be useful, but WITHOUT ANY
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// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
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// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
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//
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// A copy of the GNU General Public License is provided in the file gpl.txt. You
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// may also obtain a copy of the GNU General Public License on the World Wide
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// Web at http://www.gnu.org/licenses/gpl.html.
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//
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//******************************************************************************
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package edu.rit.util;
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/**
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* Class IdentityPair is a {@linkplain Pair Pair} with reference equality
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* semantics. Two IdentityPairs are equal if their keys refer to the same
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* object. That is, equality of keys is tested using the <TT>==</TT> operator
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* rather than the <TT>equals()</TT> method.
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* <P>
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* The key may be null. Once a key is stored in a pair, the state of the key
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* must not be altered. The value may be any object. The value may be null. Once
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* a value is stored in a pair, the state of the value may be altered, and the
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* value may be replaced by a different object.
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* <P>
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* Class IdentityPair is streamable. For object streaming to work properly, the
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* key class and the value class must be streamable or serializable.
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*
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* @param <K> Key data type.
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* @param <V> Value data type.
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*
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* @author Alan Kaminsky
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* @version 18-Jan-2015
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*/
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public class IdentityPair<K,V>
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extends Pair<K,V>
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{
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// Exported constructors.
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/**
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* Construct a new pair. The key and the value are null.
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*/
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public IdentityPair()
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{
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super();
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}
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/**
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* Construct a new pair with the given key and value.
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*
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* @param key Key.
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* @param value Value.
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*
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* @exception NullPointerException
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* (unchecked exception) Thrown if <TT>key</TT> is null.
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*/
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public IdentityPair
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(K key,
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V value)
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{
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super (key, value);
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}
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// Exported operations.
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/**
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* Determine if this pair is equal to the given object. The pairs are equal
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* if their keys refer to the same object, as determined by the <TT>==</TT>
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* operator.
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*
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* @param obj Object to test.
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*
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* @return True if this pair is equal to <TT>obj</TT>, false otherwise.
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*/
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public boolean equals
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(Object obj)
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{
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return
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(obj instanceof PairBase) &&
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(this.key == ((PairBase)obj).key);
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}
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/**
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* Returns a hash code for this pair. The hash code is that of the key, as
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* returned by the {@link System#identityHashCode(Object)
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* System.identityHashCode()} method.
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*
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* @return Hash code.
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*/
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public int hashCode()
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{
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return System.identityHashCode (key);
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}
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}
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