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Diffstat (limited to 'src/org/jivesoftware/smack/util/collections/ReferenceMap.java')
| -rw-r--r-- | src/org/jivesoftware/smack/util/collections/ReferenceMap.java | 161 |
1 files changed, 161 insertions, 0 deletions
diff --git a/src/org/jivesoftware/smack/util/collections/ReferenceMap.java b/src/org/jivesoftware/smack/util/collections/ReferenceMap.java new file mode 100644 index 0000000..f30954d --- /dev/null +++ b/src/org/jivesoftware/smack/util/collections/ReferenceMap.java @@ -0,0 +1,161 @@ +// 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); + } + +} |