Showing the changes to java/pkg/com/sun/beans/WeakCache.java (1 of 18352 files). Show all
Unified · Split
| @@ -0,0 +1,91 @@ | |||
| 1 | /* | ||
| 2 | * Copyright (c) 2008, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | package com.sun.beans; | ||
| 26 | |||
| 27 | import java.lang.ref.Reference; | ||
| 28 | import java.lang.ref.WeakReference; | ||
| 29 | |||
| 30 | import java.util.Map; | ||
| 31 | import java.util.WeakHashMap; | ||
| 32 | |||
| 33 | /** | ||
| 34 | * A hashtable-based cache with weak keys and weak values. | ||
| 35 | * An entry in the map will be automatically removed | ||
| 36 | * when its key is no longer in the ordinary use. | ||
| 37 | * A value will be automatically removed as well | ||
| 38 | * when it is no longer in the ordinary use. | ||
| 39 | * | ||
| 40 | * @since 1.7 | ||
| 41 | * | ||
| 42 | * @author Sergey A. Malenkov | ||
| 43 | */ | ||
| 44 | public final class WeakCache<K, V> { | ||
| 45 | private final Map<K, Reference<V>> map = new WeakHashMap<K, Reference<V>>(); | ||
| 46 | |||
| 47 | /** | ||
| 48 | * Returns a value to which the specified {@code key} is mapped, | ||
| 49 | * or {@code null} if this map contains no mapping for the {@code key}. | ||
| 50 | * | ||
| 51 | * @param key the key whose associated value is returned | ||
| 52 | * @return a value to which the specified {@code key} is mapped | ||
| 53 | */ | ||
| 54 | public V get(K key) { | ||
| 55 | Reference<V> reference = this.map.get(key); | ||
| 56 | if (reference == null) { | ||
| 57 | return null; | ||
| 58 | } | ||
| 59 | V value = reference.get(); | ||
| 60 | if (value == null) { | ||
| 61 | this.map.remove(key); | ||
| 62 | } | ||
| 63 | return value; | ||
| 64 | } | ||
| 65 | |||
| 66 | /** | ||
| 67 | * Associates the specified {@code value} with the specified {@code key}. | ||
| 68 | * Removes the mapping for the specified {@code key} from this cache | ||
| 69 | * if it is present and the specified {@code value} is {@code null}. | ||
| 70 | * If the cache previously contained a mapping for the {@code key}, | ||
| 71 | * the old value is replaced by the specified {@code value}. | ||
| 72 | * | ||
| 73 | * @param key the key with which the specified value is associated | ||
| 74 | * @param value the value to be associated with the specified key | ||
| 75 | */ | ||
| 76 | public void put(K key, V value) { | ||
| 77 | if (value != null) { | ||
| 78 | this.map.put(key, new WeakReference<V>(value)); | ||
| 79 | } | ||
| 80 | else { | ||
| 81 | this.map.remove(key); | ||
| 82 | } | ||
| 83 | } | ||
| 84 | |||
| 85 | /** | ||
| 86 | * Removes all of the mappings from this cache. | ||
| 87 | */ | ||
| 88 | public void clear() { | ||
| 89 | this.map.clear(); | ||
| 90 | } | ||
| 91 | } | ||