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/*
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* Copyright (c) 2010, 2011, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/*
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*******************************************************************************
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* Copyright (C) 2009-2010, International Business Machines Corporation and *
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* others. All Rights Reserved. *
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*******************************************************************************
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*/
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package sun.util.locale;
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import java.lang.ref.ReferenceQueue;
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import java.lang.ref.SoftReference;
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import java.util.concurrent.ConcurrentHashMap;
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import java.util.concurrent.ConcurrentMap;
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public abstract class LocaleObjectCache<K, V> {
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private ConcurrentMap<K, CacheEntry<K, V>> map;
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private ReferenceQueue<V> queue = new ReferenceQueue<>();
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public LocaleObjectCache() {
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this(16, 0.75f, 16);
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}
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public LocaleObjectCache(int initialCapacity, float loadFactor, int concurrencyLevel) {
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map = new ConcurrentHashMap<>(initialCapacity, loadFactor, concurrencyLevel);
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}
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public V get(K key) {
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V value = null;
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cleanStaleEntries();
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CacheEntry<K, V> entry = map.get(key);
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if (entry != null) {
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value = entry.get();
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}
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if (value == null) {
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key = normalizeKey(key);
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V newVal = createObject(key);
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if (key == null || newVal == null) {
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// subclass must return non-null key/value object
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return null;
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}
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CacheEntry<K, V> newEntry = new CacheEntry<>(key, newVal, queue);
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while (value == null) {
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cleanStaleEntries();
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entry = map.putIfAbsent(key, newEntry);
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if (entry == null) {
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value = newVal;
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break;
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} else {
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value = entry.get();
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}
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}
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}
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return value;
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}
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protected V put(K key, V value) {
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CacheEntry<K, V> entry = new CacheEntry<>(key, value, queue);
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CacheEntry<K, V> oldEntry = map.put(key, entry);
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return (oldEntry == null) ? null : oldEntry.get();
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}
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@SuppressWarnings("unchecked")
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private void cleanStaleEntries() {
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CacheEntry<K, V> entry;
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while ((entry = (CacheEntry<K, V>)queue.poll()) != null) {
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map.remove(entry.getKey());
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}
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}
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protected abstract V createObject(K key);
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protected K normalizeKey(K key) {
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return key;
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}
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private static class CacheEntry<K, V> extends SoftReference<V> {
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private K key;
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CacheEntry(K key, V value, ReferenceQueue<V> queue) {
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super(value, queue);
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this.key = key;
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}
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K getKey() {
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return key;
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}
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}
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}
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