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// GenericsNote: Converted.
/*
* Copyright 2002-2004 The Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.jivesoftware.smack.util.collections;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
/**
* A <code>Map</code> implementation that allows mappings to be
* removed by the garbage collector.
* <p/>
* When you construct a <code>ReferenceMap</code>, you can specify what kind
* of references are used to store the map's keys and values.
* If non-hard references are used, then the garbage collector can remove
* mappings if a key or value becomes unreachable, or if the JVM's memory is
* running low. For information on how the different reference types behave,
* see {@link java.lang.ref.Reference}.
* <p/>
* Different types of references can be specified for keys and values.
* The keys can be configured to be weak but the values hard,
* in which case this class will behave like a
* <a href="http://java.sun.com/j2se/1.4/docs/api/java/util/WeakHashMap.html">
* <code>WeakHashMap</code></a>. However, you can also specify hard keys and
* weak values, or any other combination. The default constructor uses
* hard keys and soft values, providing a memory-sensitive cache.
* <p/>
* This map is similar to ReferenceIdentityMap.
* It differs in that keys and values in this class are compared using <code>equals()</code>.
* <p/>
* This {@link java.util.Map} implementation does <i>not</i> allow null elements.
* Attempting to add a null key or value to the map will raise a <code>NullPointerException</code>.
* <p/>
* This implementation is not synchronized.
* You can use {@link java.util.Collections#synchronizedMap} to
* provide synchronized access to a <code>ReferenceMap</code>.
* Remember that synchronization will not stop the garbage collecter removing entries.
* <p/>
* All the available iterators can be reset back to the start by casting to
* <code>ResettableIterator</code> and calling <code>reset()</code>.
* <p/>
* NOTE: As from Commons Collections 3.1 this map extends <code>AbstractReferenceMap</code>
* (previously it extended AbstractMap). As a result, the implementation is now
* extensible and provides a <code>MapIterator</code>.
*
* @author Paul Jack
* @author Matt Hall, John Watkinson, Stephen Colebourne
* @version $Revision: 1.1 $ $Date: 2005/10/11 17:05:32 $
* @see java.lang.ref.Reference
* @since Commons Collections 3.0 (previously in main package v2.1)
*/
public class ReferenceMap <K,V> extends AbstractReferenceMap<K, V> implements Serializable {
/**
* Serialization version
*/
private static final long serialVersionUID = 1555089888138299607L;
/**
* Constructs a new <code>ReferenceMap</code> that will
* use hard references to keys and soft references to values.
*/
public ReferenceMap() {
super(HARD, SOFT, DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, false);
}
/**
* Constructs a new <code>ReferenceMap</code> that will
* use the specified types of references.
*
* @param keyType the type of reference to use for keys;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
* @param valueType the type of reference to use for values;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
*/
public ReferenceMap(int keyType, int valueType) {
super(keyType, valueType, DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, false);
}
/**
* Constructs a new <code>ReferenceMap</code> that will
* use the specified types of references.
*
* @param keyType the type of reference to use for keys;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
* @param valueType the type of reference to use for values;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
* @param purgeValues should the value be automatically purged when the
* key is garbage collected
*/
public ReferenceMap(int keyType, int valueType, boolean purgeValues) {
super(keyType, valueType, DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, purgeValues);
}
/**
* Constructs a new <code>ReferenceMap</code> with the
* specified reference types, load factor and initial
* capacity.
*
* @param keyType the type of reference to use for keys;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
* @param valueType the type of reference to use for values;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
* @param capacity the initial capacity for the map
* @param loadFactor the load factor for the map
*/
public ReferenceMap(int keyType, int valueType, int capacity, float loadFactor) {
super(keyType, valueType, capacity, loadFactor, false);
}
/**
* Constructs a new <code>ReferenceMap</code> with the
* specified reference types, load factor and initial
* capacity.
*
* @param keyType the type of reference to use for keys;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
* @param valueType the type of reference to use for values;
* must be {@link #HARD}, {@link #SOFT}, {@link #WEAK}
* @param capacity the initial capacity for the map
* @param loadFactor the load factor for the map
* @param purgeValues should the value be automatically purged when the
* key is garbage collected
*/
public ReferenceMap(int keyType, int valueType, int capacity, float loadFactor, boolean purgeValues) {
super(keyType, valueType, capacity, loadFactor, purgeValues);
}
//-----------------------------------------------------------------------
/**
* 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);
}
}
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