105 lines
3.4 KiB
Java
105 lines
3.4 KiB
Java
//******************************************************************************
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//
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// File: IdentityMap.java
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// Package: edu.rit.util
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// Unit: Class edu.rit.util.IdentityMap
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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 IdentityMap provides a mapping from keys to values with reference
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* equality semantics. Two (key, value) mappings are equal if their keys refer
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* to the same object. That is, equality of keys is tested using the <TT>==</TT>
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* operator rather than the <TT>equals()</TT> method.
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* <P>
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* Keys must not be null. Once a key is stored in a map, the state of the key
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* must not be altered. The value may be any object. Values may be null. Once a
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* value is stored in a map, 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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* The map calls the protected {@link #getPair(Object,Object) getPair()} method
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* to make (key, value) mappings (pairs). The default is to copy just the key
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* and value references. This behavior can be changed by overriding the {@link
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* #getPair(Object,Object) getPair()} method in a subclass.
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* <P>
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* Class IdentityMap is streamable. For object streaming to work properly, the
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* key and the value classes must be streamable or serializable.
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* <P>
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* <I>Note:</I> Class IdentityMap is not multiple thread safe.
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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 09-Jan-2015
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*/
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public class IdentityMap<K,V>
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extends Map<K,V>
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{
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// Exported constructors.
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/**
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* Construct a new empty map.
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*/
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public IdentityMap()
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{
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}
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/**
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* Construct a new map that is a copy of the given map.
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*
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* @param map Map to copy.
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*
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* @exception NullPointerException
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* (unchecked exception) Thrown if <TT>map</TT> is null.
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*/
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public IdentityMap
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(Map<K,V> map)
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{
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copy (map);
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}
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// Hidden operations.
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/**
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* Create a pair containing the given key and value. Whenever class
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* IdentityMap needs to create a pair, it does so by calling this method.
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* <P>
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* The <TT>getPair()</TT> method in class IdentityMap returns an instance of
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* class {@linkplain IdentityPair IdentityPair}<K,V> consisting of the
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* given <TT>key</TT> and <TT>value</TT> references.
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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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* @return Pair consisting of (key, value).
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*/
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protected Pair<K,V> getPair
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(K key,
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V value)
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{
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return new IdentityPair<K,V> (key, value);
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}
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}
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