com.twelvemonkeys.util.WeakWeakMap Maven / Gradle / Ivy
/*
* 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 "TwelveMonkeys" 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 OWNER 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.util.*;
import java.lang.ref.WeakReference;
/**
* 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 Harald Kuhr
* @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 extends WeakHashMap {
// 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 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 ref = (WeakReference) super.get(pKey);
return ref != null ? ref.get() : null;
}
@Override
public V remove(Object pKey) {
WeakReference 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 pMap) {
for (final Map.Entry entry : pMap.entrySet()) {
put(entry.getKey(), entry.getValue());
}
}
@Override
public Set> entrySet() {
return new AbstractSet>() {
public Iterator> iterator() {
return new Iterator>() {
@SuppressWarnings({"unchecked"})
final Iterator>> mIterator = (Iterator) WeakWeakMap.super.entrySet().iterator();
public boolean hasNext() {
return mIterator.hasNext();
}
public Map.Entry next() {
return new Map.Entry() {
final Map.Entry> mEntry = mIterator.next();
public K getKey() {
return mEntry.getKey();
}
public V getValue() {
WeakReference ref = mEntry.getValue();
return ref.get();
}
public V setValue(V pValue) {
WeakReference ref = mEntry.setValue(new WeakReference(pValue));
return ref != null ? ref.get() : null;
}
public boolean equals(Object obj) {
return mEntry.equals(obj);
}
public int hashCode() {
return mEntry.hashCode();
}
public String toString() {
return mEntry.toString();
}
};
}
public void remove() {
mIterator.remove();
}
};
}
public int size() {
return WeakWeakMap.this.size();
}
};
}
@Override
public Collection values() {
return new AbstractCollection() {
public Iterator iterator() {
return new Iterator() {
@SuppressWarnings({"unchecked"})
Iterator> mIterator = (Iterator>) WeakWeakMap.super.values().iterator();
public boolean hasNext() {
return mIterator.hasNext();
}
public V next() {
WeakReference ref = mIterator.next();
return ref.get();
}
public void remove() {
mIterator.remove();
}
};
}
public int size() {
return WeakWeakMap.this.size();
}
};
}
}
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