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