/*
* Copyright (c) 2008, Harald Kuhr
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* * 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.
*
* * Neither the name of the copyright holder nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS 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 COPYRIGHT HOLDER OR 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.
*/
package com.twelvemonkeys.util;
import java.lang.ref.
WeakReference;
import java.util.*;
/**
* Special-purpose map implementation with weak keys and weak values. This is
* useful for mapping between keys and values that refer to (for example by
* wrapping) their keys.
* For more info, see {@link WeakHashMap} on why the
* values in a {@code WeakHashMap} must never refer strongly to their keys.
*
* @see WeakHashMap
* @see WeakReference
*
* @author <a href="mailto:harald.kuhr@gmail.com">Harald Kuhr</a>
* @version $Id: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-core/src/main/java/com/twelvemonkeys/util/WeakWeakMap.java#1 $
*/
@
SuppressWarnings({"unchecked"})
public class
WeakWeakMap<K, V> extends
WeakHashMap<K, V> {
// TODO: Consider using a backing map and delegate, instead of extending...
/**
* Creates a {@code WeakWeakMap} with default initial capacity and load
* factor.
*
* @see java.util.WeakHashMap#WeakHashMap()
*/
public
WeakWeakMap() {
super();
}
/**
* Creates a {@code WeakWeakMap} with the given initial capacity and
* default load factor.
*
* @param pInitialCapacity the initial capacity
*
* @see java.util.WeakHashMap#WeakHashMap(int)
*/
public
WeakWeakMap(int
pInitialCapacity) {
super(
pInitialCapacity);
}
/**
* Creates a {@code WeakWeakMap} with the given initial capacity and
* load factor.
*
* @param pInitialCapacity the initial capacity
* @param pLoadFactor the load factor
*
* @see WeakHashMap#WeakHashMap(int, float)
*/
public
WeakWeakMap(int
pInitialCapacity, float
pLoadFactor) {
super(
pInitialCapacity,
pLoadFactor);
}
/**
* Creates a {@code WeakWeakMap} containing the mappings in the given map.
*
* @param pMap the map whose mappings are to be placed in this map.
*
* @see WeakHashMap#WeakHashMap(java.util.Map)
*/
public
WeakWeakMap(
Map<? extends K, ? extends V>
pMap) {
super(
pMap);
}
@
Override
public V
put(K
pKey, V
pValue) {
// NOTE: This is wrong, but we don't really care..
return super.put(
pKey, (V) new
WeakReference(
pValue));
}
@
Override
public V
get(
Object pKey) {
WeakReference<V>
ref = (
WeakReference) super.get(
pKey);
return
ref != null ?
ref.
get() : null;
}
@
Override
public V
remove(
Object pKey) {
WeakReference<V>
ref = (
WeakReference) super.remove(
pKey);
return
ref != null ?
ref.
get() : null;
}
@
Override
public boolean
containsValue(
Object pValue) {
for (final V
value :
values()) {
if (
pValue ==
value || (
value != null &&
value.
equals(
pValue))) {
return true;
}
}
return false;
}
@
Override
public void
putAll(
Map<? extends K, ? extends V>
pMap) {
for (final
Map.
Entry<? extends K, ? extends V>
entry :
pMap.
entrySet()) {
put(
entry.
getKey(),
entry.
getValue());
}
}
@
Override
public
Set<
Map.
Entry<K, V>>
entrySet() {
return new
AbstractSet<
Map.
Entry<K, V>>() {
public
Iterator<
Map.
Entry<K, V>>
iterator() {
return new
Iterator<
Map.
Entry<K, V>>() {
@
SuppressWarnings({"unchecked"})
final
Iterator<
Map.
Entry<K,
WeakReference<V>>>
iterator = (
Iterator)
WeakWeakMap.super.entrySet().
iterator();
public boolean
hasNext() {
return
iterator.
hasNext();
}
public
Map.
Entry<K, V>
next() {
return new
Map.
Entry<K, V>() {
final
Map.
Entry<K,
WeakReference<V>>
entry =
iterator.
next();
public K
getKey() {
return
entry.
getKey();
}
public V
getValue() {
WeakReference<V>
ref =
entry.
getValue();
return
ref.
get();
}
public V
setValue(V
pValue) {
WeakReference<V>
ref =
entry.
setValue(new
WeakReference<V>(
pValue));
return
ref != null ?
ref.
get() : null;
}
public boolean
equals(
Object obj) {
return
entry.
equals(
obj);
}
public int
hashCode() {
return
entry.
hashCode();
}
public
String toString() {
return
entry.
toString();
}
};
}
public void
remove() {
iterator.
remove();
}
};
}
public int
size() {
return
WeakWeakMap.this.
size();
}
};
}
@
Override
public
Collection<V>
values() {
return new
AbstractCollection<V>() {
public
Iterator<V>
iterator() {
return new
Iterator<V>() {
@
SuppressWarnings({"unchecked"})
Iterator<
WeakReference<V>>
iterator = (
Iterator<
WeakReference<V>>)
WeakWeakMap.super.values().
iterator();
public boolean
hasNext() {
return
iterator.
hasNext();
}
public V
next() {
WeakReference<V>
ref =
iterator.
next();
return
ref.
get();
}
public void
remove() {
iterator.
remove();
}
};
}
public int
size() {
return
WeakWeakMap.this.
size();
}
};
}
}