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| 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. Oracle designates this | ||
| 7 | * particular file as subject to the "Classpath" exception as provided | ||
| 8 | * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 21 | * or visit www.oracle.com if you need additional information or have any | ||
| 22 | * 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/publicdomain/zero/1.0/ | ||
| 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 | ||
| 107 | * (<a href="../Collection.html#optional-restrictions">optional</a>) | ||
| 108 | * @throws NullPointerException if the specified key or value is null, | ||
| 109 | * and this map does not permit null keys or values | ||
| 110 | * (<a href="../Collection.html#optional-restrictions">optional</a>) | ||
| 111 | */ | ||
| 112 | boolean remove(Object key, Object value); | ||
| 113 | |||
| 114 | /** | ||
| 115 | * Replaces the entry for a key only if currently mapped to a given value. | ||
| 116 | * This is equivalent to | ||
| 117 | * <pre> | ||
| 118 | * if (map.containsKey(key) && map.get(key).equals(oldValue)) { | ||
| 119 | * map.put(key, newValue); | ||
| 120 | * return true; | ||
| 121 | * } else return false;</pre> | ||
| 122 | * except that the action is performed atomically. | ||
| 123 | * | ||
| 124 | * @param key key with which the specified value is associated | ||
| 125 | * @param oldValue value expected to be associated with the specified key | ||
| 126 | * @param newValue value to be associated with the specified key | ||
| 127 | * @return <tt>true</tt> if the value was replaced | ||
| 128 | * @throws UnsupportedOperationException if the <tt>put</tt> operation | ||
| 129 | * is not supported by this map | ||
| 130 | * @throws ClassCastException if the class of a specified key or value | ||
| 131 | * prevents it from being stored in this map | ||
| 132 | * @throws NullPointerException if a specified key or value is null, | ||
| 133 | * and this map does not permit null keys or values | ||
| 134 | * @throws IllegalArgumentException if some property of a specified key | ||
| 135 | * or value prevents it from being stored in this map | ||
| 136 | */ | ||
| 137 | boolean replace(K key, V oldValue, V newValue); | ||
| 138 | |||
| 139 | /** | ||
| 140 | * Replaces the entry for a key only if currently mapped to some value. | ||
| 141 | * This is equivalent to | ||
| 142 | * <pre> | ||
| 143 | * if (map.containsKey(key)) { | ||
| 144 | * return map.put(key, value); | ||
| 145 | * } else return null;</pre> | ||
| 146 | * except that the action is performed atomically. | ||
| 147 | * | ||
| 148 | * @param key key with which the specified value is associated | ||
| 149 | * @param value value to be associated with the specified key | ||
| 150 | * @return the previous value associated with the specified key, or | ||
| 151 | * <tt>null</tt> if there was no mapping for the key. | ||
| 152 | * (A <tt>null</tt> return can also indicate that the map | ||
| 153 | * previously associated <tt>null</tt> with the key, | ||
| 154 | * if the implementation supports null values.) | ||
| 155 | * @throws UnsupportedOperationException if the <tt>put</tt> operation | ||
| 156 | * is not supported by this map | ||
| 157 | * @throws ClassCastException if the class of the specified key or value | ||
| 158 | * prevents it from being stored in this map | ||
| 159 | * @throws NullPointerException if the specified key or value is null, | ||
| 160 | * and this map does not permit null keys or values | ||
| 161 | * @throws IllegalArgumentException if some property of the specified key | ||
| 162 | * or value prevents it from being stored in this map | ||
| 163 | */ | ||
| 164 | V replace(K key, V value); | ||
| 165 | } | ||