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
 * <tt>putIfAbsent</tt>, <tt>remove</tt>, and <tt>replace</tt> 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
     *         <tt>null</tt> if there was no mapping for the key.
     *         (A <tt>null</tt> return can also indicate that the map
     *         previously associated <tt>null</tt> with the key,
     *         if the implementation supports null values.)
     * @throws UnsupportedOperationException if the <tt>put</tt> 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 <tt>true</tt> if the value was removed
     * @throws UnsupportedOperationException if the <tt>remove</tt> 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 <tt>true</tt> if the value was replaced
     * @throws UnsupportedOperationException if the <tt>put</tt> 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
     *         <tt>null</tt> if there was no mapping for the key.
     *         (A <tt>null</tt> return can also indicate that the map
     *         previously associated <tt>null</tt> with the key,
     *         if the implementation supports null values.)
     * @throws UnsupportedOperationException if the <tt>put</tt> 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:	1.37
Committed:	Sun Oct 21 06:14:12 2012 UTC (11 years, 7 months ago) by jsr166
Branch:	MAIN
Changes since 1.36:	+0 -1 lines
Log Message:	delete trailing empty lines of javadoc
#	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	import java.util.Map;
9
10	/**
11	* A {@link java.util.Map} providing additional atomic
12	* <tt>putIfAbsent</tt>, <tt>remove</tt>, and <tt>replace</tt> methods.
13	*
14	* <p>Memory consistency effects: As with other concurrent
15	* collections, actions in a thread prior to placing an object into a
16	* {@code ConcurrentMap} as a key or value
17	* <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
18	* actions subsequent to the access or removal of that object from
19	* the {@code ConcurrentMap} in another thread.
20	*
21	* <p>This interface is a member of the
22	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
23	* Java Collections Framework</a>.
24	*
25	* @since 1.5
26	* @author Doug Lea
27	* @param <K> the type of keys maintained by this map
28	* @param <V> the type of mapped values
29	*/
30	public interface ConcurrentMap<K, V> extends Map<K, V> {
31	/**
32	* If the specified key is not already associated
33	* with a value, associate it with the given value.
34	* This is equivalent to
35	* <pre> {@code
36	* if (!map.containsKey(key))
37	* return map.put(key, value);
38	* else
39	* return map.get(key);}</pre>
40	*
41	* except that the action is performed atomically.
42	*
43	* @param key key with which the specified value is to be associated
44	* @param value value to be associated with the specified key
45	* @return the previous value associated with the specified key, or
46	* <tt>null</tt> if there was no mapping for the key.
47	* (A <tt>null</tt> return can also indicate that the map
48	* previously associated <tt>null</tt> with the key,
49	* if the implementation supports null values.)
50	* @throws UnsupportedOperationException if the <tt>put</tt> operation
51	* is not supported by this map
52	* @throws ClassCastException if the class of the specified key or value
53	* prevents it from being stored in this map
54	* @throws NullPointerException if the specified key or value is null,
55	* and this map does not permit null keys or values
56	* @throws IllegalArgumentException if some property of the specified key
57	* or value prevents it from being stored in this map
58	*/
59	V putIfAbsent(K key, V value);
60
61	/**
62	* Removes the entry for a key only if currently mapped to a given value.
63	* This is equivalent to
64	* <pre> {@code
65	* if (map.containsKey(key) && map.get(key).equals(value)) {
66	* map.remove(key);
67	* return true;
68	* } else
69	* return false;}</pre>
70	*
71	* except that the action is performed atomically.
72	*
73	* @param key key with which the specified value is associated
74	* @param value value expected to be associated with the specified key
75	* @return <tt>true</tt> if the value was removed
76	* @throws UnsupportedOperationException if the <tt>remove</tt> operation
77	* is not supported by this map
78	* @throws ClassCastException if the key or value is of an inappropriate
79	* type for this map
80	* (<a href="../Collection.html#optional-restrictions">optional</a>)
81	* @throws NullPointerException if the specified key or value is null,
82	* and this map does not permit null keys or values
83	* (<a href="../Collection.html#optional-restrictions">optional</a>)
84	*/
85	boolean remove(Object key, Object value);
86
87	/**
88	* Replaces the entry for a key only if currently mapped to a given value.
89	* This is equivalent to
90	* <pre> {@code
91	* if (map.containsKey(key) && map.get(key).equals(oldValue)) {
92	* map.put(key, newValue);
93	* return true;
94	* } else
95	* return false;}</pre>
96	*
97	* except that the action is performed atomically.
98	*
99	* @param key key with which the specified value is associated
100	* @param oldValue value expected to be associated with the specified key
101	* @param newValue value to be associated with the specified key
102	* @return <tt>true</tt> if the value was replaced
103	* @throws UnsupportedOperationException if the <tt>put</tt> operation
104	* is not supported by this map
105	* @throws ClassCastException if the class of a specified key or value
106	* prevents it from being stored in this map
107	* @throws NullPointerException if a specified key or value is null,
108	* and this map does not permit null keys or values
109	* @throws IllegalArgumentException if some property of a specified key
110	* or value prevents it from being stored in this map
111	*/
112	boolean replace(K key, V oldValue, V newValue);
113
114	/**
115	* Replaces the entry for a key only if currently mapped to some value.
116	* This is equivalent to
117	* <pre> {@code
118	* if (map.containsKey(key)) {
119	* return map.put(key, value);
120	* } else
121	* return null;}</pre>
122	*
123	* except that the action is performed atomically.
124	*
125	* @param key key with which the specified value is associated
126	* @param value value to be associated with the specified key
127	* @return the previous value associated with the specified key, or
128	* <tt>null</tt> if there was no mapping for the key.
129	* (A <tt>null</tt> return can also indicate that the map
130	* previously associated <tt>null</tt> with the key,
131	* if the implementation supports null values.)
132	* @throws UnsupportedOperationException if the <tt>put</tt> operation
133	* is not supported by this map
134	* @throws ClassCastException if the class of the specified key or value
135	* prevents it from being stored in this map
136	* @throws NullPointerException if the specified key or value is null,
137	* and this map does not permit null keys or values
138	* @throws IllegalArgumentException if some property of the specified key
139	* or value prevents it from being stored in this map
140	*/
141	V replace(K key, V value);
142	}