util/concurrent/ConcurrentMap.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */

package java.util.concurrent;

import java.util.Map;

/**
 * A {@link java.util.Map} providing additional atomic
 * {@code putIfAbsent}, {@code remove}, and {@code replace} methods.
 *
 * <p>Memory consistency effects: As with other concurrent
 * collections, actions in a thread prior to placing an object into a
 * {@code ConcurrentMap} as a key or value
 * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
 * actions subsequent to the access or removal of that object from
 * the {@code ConcurrentMap} in another thread.
 *
 * <p>This interface is a member of the
 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
 * Java Collections Framework</a>.
 *
 * @since 1.5
 * @author Doug Lea
 * @param <K> the type of keys maintained by this map
 * @param <V> the type of mapped values
 */
public interface ConcurrentMap<K,V> extends Map<K,V> {
    /**
     * If the specified key is not already associated
     * with a value, associate it with the given value.
     * This is equivalent to
     *  <pre> {@code
     * if (!map.containsKey(key))
     *   return map.put(key, value);
     * else
     *   return map.get(key);}</pre>
     *
     * except that the action is performed atomically.
     *
     * @param key key with which the specified value is to be associated
     * @param value value to be associated with the specified key
     * @return the previous value associated with the specified key, or
     *         {@code null} if there was no mapping for the key.
     *         (A {@code null} return can also indicate that the map
     *         previously associated {@code null} with the key,
     *         if the implementation supports null values.)
     * @throws UnsupportedOperationException if the {@code put} operation
     *         is not supported by this map
     * @throws ClassCastException if the class of the specified key or value
     *         prevents it from being stored in this map
     * @throws NullPointerException if the specified key or value is null,
     *         and this map does not permit null keys or values
     * @throws IllegalArgumentException if some property of the specified key
     *         or value prevents it from being stored in this map
     */
    V putIfAbsent(K key, V value);

    /**
     * Removes the entry for a key only if currently mapped to a given value.
     * This is equivalent to
     *  <pre> {@code
     * if (map.containsKey(key) && map.get(key).equals(value)) {
     *   map.remove(key);
     *   return true;
     * } else
     *   return false;}</pre>
     *
     * except that the action is performed atomically.
     *
     * @param key key with which the specified value is associated
     * @param value value expected to be associated with the specified key
     * @return {@code true} if the value was removed
     * @throws UnsupportedOperationException if the {@code remove} operation
     *         is not supported by this map
     * @throws ClassCastException if the key or value is of an inappropriate
     *         type for this map
     *         (<a href="../Collection.html#optional-restrictions">optional</a>)
     * @throws NullPointerException if the specified key or value is null,
     *         and this map does not permit null keys or values
     *         (<a href="../Collection.html#optional-restrictions">optional</a>)
     */
    boolean remove(Object key, Object value);

    /**
     * Replaces the entry for a key only if currently mapped to a given value.
     * This is equivalent to
     *  <pre> {@code
     * if (map.containsKey(key) && map.get(key).equals(oldValue)) {
     *   map.put(key, newValue);
     *   return true;
     * } else
     *   return false;}</pre>
     *
     * except that the action is performed atomically.
     *
     * @param key key with which the specified value is associated
     * @param oldValue value expected to be associated with the specified key
     * @param newValue value to be associated with the specified key
     * @return {@code true} if the value was replaced
     * @throws UnsupportedOperationException if the {@code put} operation
     *         is not supported by this map
     * @throws ClassCastException if the class of a specified key or value
     *         prevents it from being stored in this map
     * @throws NullPointerException if a specified key or value is null,
     *         and this map does not permit null keys or values
     * @throws IllegalArgumentException if some property of a specified key
     *         or value prevents it from being stored in this map
     */
    boolean replace(K key, V oldValue, V newValue);

    /**
     * Replaces the entry for a key only if currently mapped to some value.
     * This is equivalent to
     *  <pre> {@code
     * if (map.containsKey(key)) {
     *   return map.put(key, value);
     * } else
     *   return null;}</pre>
     *
     * except that the action is performed atomically.
     *
     * @param key key with which the specified value is associated
     * @param value value to be associated with the specified key
     * @return the previous value associated with the specified key, or
     *         {@code null} if there was no mapping for the key.
     *         (A {@code null} return can also indicate that the map
     *         previously associated {@code null} with the key,
     *         if the implementation supports null values.)
     * @throws UnsupportedOperationException if the {@code put} operation
     *         is not supported by this map
     * @throws ClassCastException if the class of the specified key or value
     *         prevents it from being stored in this map
     * @throws NullPointerException if the specified key or value is null,
     *         and this map does not permit null keys or values
     * @throws IllegalArgumentException if some property of the specified key
     *         or value prevents it from being stored in this map
     */
    V replace(K key, V value);
}
Revision:	1.4
Committed:	Sun Jan 18 20:17:32 2015 UTC (9 years, 5 months ago) by jsr166
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.3:	+1 -0 lines
Log Message:	exactly one blank line before and after package statements
#	User	Rev	Content
1	dl	1.1	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3			* Expert Group and released to the public domain, as explained at
4			* http://creativecommons.org/publicdomain/zero/1.0/
5			*/
6
7			package java.util.concurrent;
8	jsr166	1.4
9	dl	1.1	import java.util.Map;
10
11			/**
12			* A {@link java.util.Map} providing additional atomic
13	jsr166	1.2	* {@code putIfAbsent}, {@code remove}, and {@code replace} methods.
14	dl	1.1	*
15			* <p>Memory consistency effects: As with other concurrent
16			* collections, actions in a thread prior to placing an object into a
17			* {@code ConcurrentMap} as a key or value
18			* <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
19			* actions subsequent to the access or removal of that object from
20			* the {@code ConcurrentMap} in another thread.
21			*
22			* <p>This interface is a member of the
23			* <a href="{@docRoot}/../technotes/guides/collections/index.html">
24			* Java Collections Framework</a>.
25			*
26			* @since 1.5
27			* @author Doug Lea
28			* @param <K> the type of keys maintained by this map
29			* @param <V> the type of mapped values
30			*/
31	jsr166	1.3	public interface ConcurrentMap<K,V> extends Map<K,V> {
32	dl	1.1	/**
33			* If the specified key is not already associated
34			* with a value, associate it with the given value.
35			* This is equivalent to
36			* <pre> {@code
37			* if (!map.containsKey(key))
38			* return map.put(key, value);
39			* else
40			* return map.get(key);}</pre>
41			*
42			* except that the action is performed atomically.
43			*
44			* @param key key with which the specified value is to be associated
45			* @param value value to be associated with the specified key
46			* @return the previous value associated with the specified key, or
47	jsr166	1.2	* {@code null} if there was no mapping for the key.
48			* (A {@code null} return can also indicate that the map
49			* previously associated {@code null} with the key,
50	dl	1.1	* if the implementation supports null values.)
51	jsr166	1.2	* @throws UnsupportedOperationException if the {@code put} operation
52	dl	1.1	* is not supported by this map
53			* @throws ClassCastException if the class of the specified key or value
54			* prevents it from being stored in this map
55			* @throws NullPointerException if the specified key or value is null,
56			* and this map does not permit null keys or values
57			* @throws IllegalArgumentException if some property of the specified key
58			* or value prevents it from being stored in this map
59			*/
60			V putIfAbsent(K key, V value);
61
62			/**
63			* Removes the entry for a key only if currently mapped to a given value.
64			* This is equivalent to
65			* <pre> {@code
66			* if (map.containsKey(key) && map.get(key).equals(value)) {
67			* map.remove(key);
68			* return true;
69			* } else
70			* return false;}</pre>
71			*
72			* except that the action is performed atomically.
73			*
74			* @param key key with which the specified value is associated
75			* @param value value expected to be associated with the specified key
76	jsr166	1.2	* @return {@code true} if the value was removed
77			* @throws UnsupportedOperationException if the {@code remove} operation
78	dl	1.1	* is not supported by this map
79			* @throws ClassCastException if the key or value is of an inappropriate
80			* type for this map
81			* (<a href="../Collection.html#optional-restrictions">optional</a>)
82			* @throws NullPointerException if the specified key or value is null,
83			* and this map does not permit null keys or values
84			* (<a href="../Collection.html#optional-restrictions">optional</a>)
85			*/
86			boolean remove(Object key, Object value);
87
88			/**
89			* Replaces the entry for a key only if currently mapped to a given value.
90			* This is equivalent to
91			* <pre> {@code
92			* if (map.containsKey(key) && map.get(key).equals(oldValue)) {
93			* map.put(key, newValue);
94			* return true;
95			* } else
96			* return false;}</pre>
97			*
98			* except that the action is performed atomically.
99			*
100			* @param key key with which the specified value is associated
101			* @param oldValue value expected to be associated with the specified key
102			* @param newValue value to be associated with the specified key
103	jsr166	1.2	* @return {@code true} if the value was replaced
104			* @throws UnsupportedOperationException if the {@code put} operation
105	dl	1.1	* is not supported by this map
106			* @throws ClassCastException if the class of a specified key or value
107			* prevents it from being stored in this map
108			* @throws NullPointerException if a specified key or value is null,
109			* and this map does not permit null keys or values
110			* @throws IllegalArgumentException if some property of a specified key
111			* or value prevents it from being stored in this map
112			*/
113			boolean replace(K key, V oldValue, V newValue);
114
115			/**
116			* Replaces the entry for a key only if currently mapped to some value.
117			* This is equivalent to
118			* <pre> {@code
119			* if (map.containsKey(key)) {
120			* return map.put(key, value);
121			* } else
122			* return null;}</pre>
123			*
124			* except that the action is performed atomically.
125			*
126			* @param key key with which the specified value is associated
127			* @param value value to be associated with the specified key
128			* @return the previous value associated with the specified key, or
129	jsr166	1.2	* {@code null} if there was no mapping for the key.
130			* (A {@code null} return can also indicate that the map
131			* previously associated {@code null} with the key,
132	dl	1.1	* if the implementation supports null values.)
133	jsr166	1.2	* @throws UnsupportedOperationException if the {@code put} operation
134	dl	1.1	* is not supported by this map
135			* @throws ClassCastException if the class of the specified key or value
136			* prevents it from being stored in this map
137			* @throws NullPointerException if the specified key or value is null,
138			* and this map does not permit null keys or values
139			* @throws IllegalArgumentException if some property of the specified key
140			* or value prevents it from being stored in this map
141			*/
142			V replace(K key, V value);
143			}