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/*
* Copyright (C) 2010 The Android Open Source Project
*
* 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 com.android.gallery3d.util;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Set;
public class IdentityCache<K, V> {
private final HashMap<K, Entry<K, V>> mWeakMap =
new HashMap<K, Entry<K, V>>();
private ReferenceQueue<V> mQueue = new ReferenceQueue<V>();
public IdentityCache() {
}
private static class Entry<K, V> extends WeakReference<V> {
K mKey;
public Entry(K key, V value, ReferenceQueue<V> queue) {
super(value, queue);
mKey = key;
}
}
private void cleanUpWeakMap() {
Entry<K, V> entry = (Entry<K, V>) mQueue.poll();
while (entry != null) {
mWeakMap.remove(entry.mKey);
entry = (Entry<K, V>) mQueue.poll();
}
}
public synchronized V put(K key, V value) {
cleanUpWeakMap();
Entry<K, V> entry = mWeakMap.put(
key, new Entry<K, V>(key, value, mQueue));
return entry == null ? null : entry.get();
}
public synchronized V get(K key) {
cleanUpWeakMap();
Entry<K, V> entry = mWeakMap.get(key);
return entry == null ? null : entry.get();
}
// This is currently unused.
/*
public synchronized void clear() {
mWeakMap.clear();
mQueue = new ReferenceQueue<V>();
}
*/
// This is for debugging only
public synchronized ArrayList<K> keys() {
Set<K> set = mWeakMap.keySet();
ArrayList<K> result = new ArrayList<K>(set);
return result;
}
}
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