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/*
* Copyright (c) 2005-2019 Radiance Kirill Grouchnikov. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* o Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* o 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.
*
* o 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 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 org.pushingpixels.substance.internal.utils;
import java.io.Serializable;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.util.*;
/**
* The original implementation is taken from The Java
* Specialists' Newsletter [Issue 098] with permission of the original
* author. Tweaked code by Endre Stolsvik was contributed in December 2009.
*
* @author Dr. Heinz M. Kabutz
* @author Endre Stolsvik
*/
class SoftHashMap extends AbstractMap implements Serializable {
/** The internal HashMap that will hold the SoftReference. */
private final Map> hash = new HashMap>();
/** Reference queue for cleared SoftReference objects. */
private final ReferenceQueue queue = new ReferenceQueue();
public static class KeySoftReference extends SoftReference {
final K key;
public KeySoftReference(K key, V referent, ReferenceQueue q) {
super(referent, q);
this.key = key;
}
}
@Override
public V get(Object key) {
expungeStaleEntries();
V result = null;
// We get the SoftReference represented by that key
KeySoftReference soft_ref = hash.get(key);
if (soft_ref != null) {
// From the SoftReference we get the value, which can be
// null if it has been garbage collected
result = soft_ref.get();
if (result == null) {
// If the value has been garbage collected, remove the
// entry from the HashMap.
hash.remove(key);
}
}
return result;
}
private void expungeStaleEntries() {
Reference ref;
while ((ref = queue.poll()) != null) {
KeySoftReference keyRef = (KeySoftReference) ref;
hash.remove(keyRef.key);
}
}
@Override
public V put(K key, V value) {
expungeStaleEntries();
KeySoftReference keyRef = new KeySoftReference(key, value,
queue);
SoftReference result = hash.put(key, keyRef);
if (result == null)
return null;
return result.get();
}
@Override
public V remove(Object key) {
expungeStaleEntries();
SoftReference result = hash.remove(key);
if (result == null)
return null;
return result.get();
}
@Override
public void clear() {
hash.clear();
}
@Override
public int size() {
expungeStaleEntries();
return hash.size();
}
@Override
public boolean containsKey(Object key) {
expungeStaleEntries();
SoftReference keyRef = hash.get(key);
if (keyRef != null) {
// From the SoftReference we get the value, which can be
// null if it has been garbage collected
V result = keyRef.get();
if (result != null) {
return true;
}
// If the value has been garbage collected, remove the
// entry from the HashMap.
hash.remove(key);
}
return false;
}
/**
* Returns a copy of the key/values in the map at the point of calling.
* However, setValue still sets the value in the actual SoftHashMap.
*/
@Override
public Set> entrySet() {
expungeStaleEntries();
Set> result = new LinkedHashSet>();
for (final Entry> entry : hash.entrySet()) {
final V value = entry.getValue().get();
if (value != null) {
result.add(new Entry() {
public K getKey() {
return entry.getKey();
}
public V getValue() {
return value;
}
public V setValue(V v) {
entry.setValue(new KeySoftReference(entry
.getKey(), v, queue));
return value;
}
});
}
}
return result;
}
}
