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, 4 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
#	Content
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
9	import java.util.Map;
10
11	/**
12	* A {@link java.util.Map} providing additional atomic
13	* {@code putIfAbsent}, {@code remove}, and {@code replace} methods.
14	*
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	public interface ConcurrentMap<K,V> extends Map<K,V> {
32	/**
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	* {@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	* if the implementation supports null values.)
51	* @throws UnsupportedOperationException if the {@code put} operation
52	* 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	* @return {@code true} if the value was removed
77	* @throws UnsupportedOperationException if the {@code remove} operation
78	* 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	* @return {@code true} if the value was replaced
104	* @throws UnsupportedOperationException if the {@code put} operation
105	* 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	* {@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	* if the implementation supports null values.)
133	* @throws UnsupportedOperationException if the {@code put} operation
134	* 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	}