J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 3 | * |
| 4 | * This code is free software; you can redistribute it and/or modify it |
| 5 | * under the terms of the GNU General Public License version 2 only, as |
| 6 | * published by the Free Software Foundation. Sun designates this |
| 7 | * particular file as subject to the "Classpath" exception as provided |
| 8 | * by Sun in the LICENSE file that accompanied this code. |
| 9 | * |
| 10 | * This code is distributed in the hope that it will be useful, but WITHOUT |
| 11 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 12 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 13 | * version 2 for more details (a copy is included in the LICENSE file that |
| 14 | * accompanied this code). |
| 15 | * |
| 16 | * You should have received a copy of the GNU General Public License version |
| 17 | * 2 along with this work; if not, write to the Free Software Foundation, |
| 18 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| 19 | * |
| 20 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 21 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 22 | * have any questions. |
| 23 | */ |
| 24 | |
| 25 | /* |
| 26 | * This file is available under and governed by the GNU General Public |
| 27 | * License version 2 only, as published by the Free Software Foundation. |
| 28 | * However, the following notice accompanied the original version of this |
| 29 | * file: |
| 30 | * |
| 31 | * Written by Doug Lea with assistance from members of JCP JSR-166 |
| 32 | * Expert Group and released to the public domain, as explained at |
| 33 | * http://creativecommons.org/licenses/publicdomain |
| 34 | */ |
| 35 | |
| 36 | package java.util.concurrent; |
| 37 | import java.util.Map; |
| 38 | |
| 39 | /** |
| 40 | * A {@link java.util.Map} providing additional atomic |
| 41 | * <tt>putIfAbsent</tt>, <tt>remove</tt>, and <tt>replace</tt> methods. |
| 42 | * |
| 43 | * <p>Memory consistency effects: As with other concurrent |
| 44 | * collections, actions in a thread prior to placing an object into a |
| 45 | * {@code ConcurrentMap} as a key or value |
| 46 | * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a> |
| 47 | * actions subsequent to the access or removal of that object from |
| 48 | * the {@code ConcurrentMap} in another thread. |
| 49 | * |
| 50 | * <p>This interface is a member of the |
| 51 | * <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
| 52 | * Java Collections Framework</a>. |
| 53 | * |
| 54 | * @since 1.5 |
| 55 | * @author Doug Lea |
| 56 | * @param <K> the type of keys maintained by this map |
| 57 | * @param <V> the type of mapped values |
| 58 | */ |
| 59 | public interface ConcurrentMap<K, V> extends Map<K, V> { |
| 60 | /** |
| 61 | * If the specified key is not already associated |
| 62 | * with a value, associate it with the given value. |
| 63 | * This is equivalent to |
| 64 | * <pre> |
| 65 | * if (!map.containsKey(key)) |
| 66 | * return map.put(key, value); |
| 67 | * else |
| 68 | * return map.get(key);</pre> |
| 69 | * except that the action is performed atomically. |
| 70 | * |
| 71 | * @param key key with which the specified value is to be associated |
| 72 | * @param value value to be associated with the specified key |
| 73 | * @return the previous value associated with the specified key, or |
| 74 | * <tt>null</tt> if there was no mapping for the key. |
| 75 | * (A <tt>null</tt> return can also indicate that the map |
| 76 | * previously associated <tt>null</tt> with the key, |
| 77 | * if the implementation supports null values.) |
| 78 | * @throws UnsupportedOperationException if the <tt>put</tt> operation |
| 79 | * is not supported by this map |
| 80 | * @throws ClassCastException if the class of the specified key or value |
| 81 | * prevents it from being stored in this map |
| 82 | * @throws NullPointerException if the specified key or value is null, |
| 83 | * and this map does not permit null keys or values |
| 84 | * @throws IllegalArgumentException if some property of the specified key |
| 85 | * or value prevents it from being stored in this map |
| 86 | * |
| 87 | */ |
| 88 | V putIfAbsent(K key, V value); |
| 89 | |
| 90 | /** |
| 91 | * Removes the entry for a key only if currently mapped to a given value. |
| 92 | * This is equivalent to |
| 93 | * <pre> |
| 94 | * if (map.containsKey(key) && map.get(key).equals(value)) { |
| 95 | * map.remove(key); |
| 96 | * return true; |
| 97 | * } else return false;</pre> |
| 98 | * except that the action is performed atomically. |
| 99 | * |
| 100 | * @param key key with which the specified value is associated |
| 101 | * @param value value expected to be associated with the specified key |
| 102 | * @return <tt>true</tt> if the value was removed |
| 103 | * @throws UnsupportedOperationException if the <tt>remove</tt> operation |
| 104 | * is not supported by this map |
| 105 | * @throws ClassCastException if the key or value is of an inappropriate |
| 106 | * type for this map (optional) |
| 107 | * @throws NullPointerException if the specified key or value is null, |
| 108 | * and this map does not permit null keys or values (optional) |
| 109 | */ |
| 110 | boolean remove(Object key, Object value); |
| 111 | |
| 112 | /** |
| 113 | * Replaces the entry for a key only if currently mapped to a given value. |
| 114 | * This is equivalent to |
| 115 | * <pre> |
| 116 | * if (map.containsKey(key) && map.get(key).equals(oldValue)) { |
| 117 | * map.put(key, newValue); |
| 118 | * return true; |
| 119 | * } else return false;</pre> |
| 120 | * except that the action is performed atomically. |
| 121 | * |
| 122 | * @param key key with which the specified value is associated |
| 123 | * @param oldValue value expected to be associated with the specified key |
| 124 | * @param newValue value to be associated with the specified key |
| 125 | * @return <tt>true</tt> if the value was replaced |
| 126 | * @throws UnsupportedOperationException if the <tt>put</tt> operation |
| 127 | * is not supported by this map |
| 128 | * @throws ClassCastException if the class of a specified key or value |
| 129 | * prevents it from being stored in this map |
| 130 | * @throws NullPointerException if a specified key or value is null, |
| 131 | * and this map does not permit null keys or values |
| 132 | * @throws IllegalArgumentException if some property of a specified key |
| 133 | * or value prevents it from being stored in this map |
| 134 | */ |
| 135 | boolean replace(K key, V oldValue, V newValue); |
| 136 | |
| 137 | /** |
| 138 | * Replaces the entry for a key only if currently mapped to some value. |
| 139 | * This is equivalent to |
| 140 | * <pre> |
| 141 | * if (map.containsKey(key)) { |
| 142 | * return map.put(key, value); |
| 143 | * } else return null;</pre> |
| 144 | * except that the action is performed atomically. |
| 145 | * |
| 146 | * @param key key with which the specified value is associated |
| 147 | * @param value value to be associated with the specified key |
| 148 | * @return the previous value associated with the specified key, or |
| 149 | * <tt>null</tt> if there was no mapping for the key. |
| 150 | * (A <tt>null</tt> return can also indicate that the map |
| 151 | * previously associated <tt>null</tt> with the key, |
| 152 | * if the implementation supports null values.) |
| 153 | * @throws UnsupportedOperationException if the <tt>put</tt> operation |
| 154 | * is not supported by this map |
| 155 | * @throws ClassCastException if the class of the specified key or value |
| 156 | * prevents it from being stored in this map |
| 157 | * @throws NullPointerException if the specified key or value is null, |
| 158 | * and this map does not permit null keys or values |
| 159 | * @throws IllegalArgumentException if some property of the specified key |
| 160 | * or value prevents it from being stored in this map |
| 161 | */ |
| 162 | V replace(K key, V value); |
| 163 | } |