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/* ====================================================================
* The Apache Software License, Version 1.1
*
* Copyright (c) 2003-2004 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowledgement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowledgement may appear in the software itself,
* if and wherever such third-party acknowledgements normally appear.
*
* 4. The names "The Jakarta Project", "Commons", and "Apache Software
* Foundation" must not be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact [email protected].
*
* 5. Products derived from this software may not be called "Apache"
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*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* Map implementation that matches keys and values based
* on == not equals().
*
* This map will violate the detail of various Map and map view contracts.
* As a general rule, don't compare this map to other maps.
*
* @since Commons Collections 3.0
* @version $Revision: 1.4 $ $Date: 2004/01/14 21:43:11 $
*
* @author java util HashMap
* @author Stephen Colebourne
*/
public class IdentityMap
extends AbstractHashedMap implements Serializable, Cloneable {
/** Serialisation version */
private static final long serialVersionUID = 2028493495224302329L;
/**
* Constructs a new empty map with default size and load factor.
*/
public IdentityMap() {
super(DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_THRESHOLD);
}
/**
* Constructs a new, empty map with the specified initial capacity.
*
* @param initialCapacity the initial capacity
* @throws IllegalArgumentException if the initial capacity is less than one
*/
public IdentityMap(int initialCapacity) {
super(initialCapacity);
}
/**
* Constructs a new, empty map with the specified initial capacity and
* load factor.
*
* @param initialCapacity the initial capacity
* @param loadFactor the load factor
* @throws IllegalArgumentException if the initial capacity is less than one
* @throws IllegalArgumentException if the load factor is less than zero
*/
public IdentityMap(int initialCapacity, float loadFactor) {
super(initialCapacity, loadFactor);
}
/**
* Constructor copying elements from another map.
*
* @param map the map to copy
* @throws NullPointerException if the map is null
*/
public IdentityMap(Map map) {
super(map);
}
//-----------------------------------------------------------------------
/**
* Gets the hash code for the key specified.
* This implementation uses the identity hash code.
*
* @param key the key to get a hash code for
* @return the hash code
*/
protected int hash(Object key) {
return System.identityHashCode(key);
}
/**
* Compares two keys for equals.
* This implementation uses ==.
*
* @param key1 the first key to compare
* @param key2 the second key to compare
* @return true if equal by identity
*/
protected boolean isEqualKey(Object key1, Object key2) {
return (key1 == key2);
}
/**
* Compares two values for equals.
* This implementation uses ==.
*
* @param value1 the first value to compare
* @param value2 the second value to compare
* @return true if equal by identity
*/
protected boolean isEqualValue(Object value1, Object value2) {
return (value1 == value2);
}
/**
* Creates an entry to store the data.
* This implementation creates an IdentityEntry instance.
*
* @param next the next entry in sequence
* @param hashCode the hash code to use
* @param key the key to store
* @param value the value to store
* @return the newly created entry
*/
protected HashEntry createEntry(HashEntry next, int hashCode, Object key, Object value) {
return new IdentityEntry(next, hashCode, key, value);
}
//-----------------------------------------------------------------------
/**
* HashEntry
*/
protected static class IdentityEntry extends HashEntry {
protected IdentityEntry(HashEntry next, int hashCode, Object key, Object value) {
super(next, hashCode, key, value);
}
public boolean equals(Object obj) {
if (obj == this) {
return true;
}
if (obj instanceof Map.Entry == false) {
return false;
}
Map.Entry other = (Map.Entry) obj;
return
(getKey() == other.getKey()) &&
(getValue() == other.getValue());
}
public int hashCode() {
return System.identityHashCode(getKey()) ^
System.identityHashCode(getValue());
}
}
//-----------------------------------------------------------------------
/**
* Clones the map without cloning the keys or values.
*
* @return a shallow clone
*/
public Object clone() {
return super.clone();
}
/**
* Write the map out using a custom routine.
*/
private void writeObject(ObjectOutputStream out) throws IOException {
out.defaultWriteObject();
doWriteObject(out);
}
/**
* Read the map in using a custom routine.
*/
private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
in.defaultReadObject();
doReadObject(in);
}
}