1 /* 2 * Copyright (C) 2010 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.android.gallery3d.util; 18 19 import java.lang.ref.ReferenceQueue; 20 import java.lang.ref.WeakReference; 21 import java.util.HashMap; 22 import java.util.ArrayList; 23 import java.util.Set; 24 25 public class IdentityCache<K, V> { 26 27 private final HashMap<K, Entry<K, V>> mWeakMap = 28 new HashMap<K, Entry<K, V>>(); 29 private ReferenceQueue<V> mQueue = new ReferenceQueue<V>(); 30 31 public IdentityCache() { 32 } 33 34 private static class Entry<K, V> extends WeakReference<V> { 35 K mKey; 36 37 public Entry(K key, V value, ReferenceQueue<V> queue) { 38 super(value, queue); 39 mKey = key; 40 } 41 } 42 43 private void cleanUpWeakMap() { 44 Entry<K, V> entry = (Entry<K, V>) mQueue.poll(); 45 while (entry != null) { 46 mWeakMap.remove(entry.mKey); 47 entry = (Entry<K, V>) mQueue.poll(); 48 } 49 } 50 51 public synchronized V put(K key, V value) { 52 cleanUpWeakMap(); 53 Entry<K, V> entry = mWeakMap.put( 54 key, new Entry<K, V>(key, value, mQueue)); 55 return entry == null ? null : entry.get(); 56 } 57 58 public synchronized V get(K key) { 59 cleanUpWeakMap(); 60 Entry<K, V> entry = mWeakMap.get(key); 61 return entry == null ? null : entry.get(); 62 } 63 64 public synchronized void clear() { 65 mWeakMap.clear(); 66 mQueue = new ReferenceQueue<V>(); 67 } 68 69 public synchronized ArrayList<K> keys() { 70 Set<K> set = mWeakMap.keySet(); 71 ArrayList<K> result = new ArrayList<K>(set); 72 return result; 73 } 74 } 75
