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>
     *   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>
     *   if (map.containsKey(key) &amp;&amp; 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>
     *   if (map.containsKey(key) &amp;&amp; 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>
     *   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:	1.35
Committed:	Fri Apr 22 01:09:27 2011 UTC (13 years, 1 month ago) by jsr166
Branch:	MAIN
CVS Tags:	release-1_7_0
Changes since 1.34:	+1 -1 lines
Log Message:	whitespace
#	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>
36	* if (!map.containsKey(key))
37	* return map.put(key, value);
38	* else
39	* return map.get(key);</pre>
40	* except that the action is performed atomically.
41	*
42	* @param key key with which the specified value is to be associated
43	* @param value value to be associated with the specified key
44	* @return the previous value associated with the specified key, or
45	* <tt>null</tt> if there was no mapping for the key.
46	* (A <tt>null</tt> return can also indicate that the map
47	* previously associated <tt>null</tt> with the key,
48	* if the implementation supports null values.)
49	* @throws UnsupportedOperationException if the <tt>put</tt> operation
50	* is not supported by this map
51	* @throws ClassCastException if the class of the specified key or value
52	* prevents it from being stored in this map
53	* @throws NullPointerException if the specified key or value is null,
54	* and this map does not permit null keys or values
55	* @throws IllegalArgumentException if some property of the specified key
56	* or value prevents it from being stored in this map
57	*
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>
65	* if (map.containsKey(key) && map.get(key).equals(value)) {
66	* map.remove(key);
67	* return true;
68	* } else return false;</pre>
69	* except that the action is performed atomically.
70	*
71	* @param key key with which the specified value is associated
72	* @param value value expected to be associated with the specified key
73	* @return <tt>true</tt> if the value was removed
74	* @throws UnsupportedOperationException if the <tt>remove</tt> operation
75	* is not supported by this map
76	* @throws ClassCastException if the key or value is of an inappropriate
77	* type for this map
78	* (<a href="../Collection.html#optional-restrictions">optional</a>)
79	* @throws NullPointerException if the specified key or value is null,
80	* and this map does not permit null keys or values
81	* (<a href="../Collection.html#optional-restrictions">optional</a>)
82	*/
83	boolean remove(Object key, Object value);
84
85	/**
86	* Replaces the entry for a key only if currently mapped to a given value.
87	* This is equivalent to
88	* <pre>
89	* if (map.containsKey(key) && map.get(key).equals(oldValue)) {
90	* map.put(key, newValue);
91	* return true;
92	* } else return false;</pre>
93	* except that the action is performed atomically.
94	*
95	* @param key key with which the specified value is associated
96	* @param oldValue value expected to be associated with the specified key
97	* @param newValue value to be associated with the specified key
98	* @return <tt>true</tt> if the value was replaced
99	* @throws UnsupportedOperationException if the <tt>put</tt> operation
100	* is not supported by this map
101	* @throws ClassCastException if the class of a specified key or value
102	* prevents it from being stored in this map
103	* @throws NullPointerException if a specified key or value is null,
104	* and this map does not permit null keys or values
105	* @throws IllegalArgumentException if some property of a specified key
106	* or value prevents it from being stored in this map
107	*/
108	boolean replace(K key, V oldValue, V newValue);
109
110	/**
111	* Replaces the entry for a key only if currently mapped to some value.
112	* This is equivalent to
113	* <pre>
114	* if (map.containsKey(key)) {
115	* return map.put(key, value);
116	* } else return null;</pre>
117	* except that the action is performed atomically.
118	*
119	* @param key key with which the specified value is associated
120	* @param value value to be associated with the specified key
121	* @return the previous value associated with the specified key, or
122	* <tt>null</tt> if there was no mapping for the key.
123	* (A <tt>null</tt> return can also indicate that the map
124	* previously associated <tt>null</tt> with the key,
125	* if the implementation supports null values.)
126	* @throws UnsupportedOperationException if the <tt>put</tt> operation
127	* is not supported by this map
128	* @throws ClassCastException if the class of the specified key or value
129	* prevents it from being stored in this map
130	* @throws NullPointerException if the specified key or value is null,
131	* and this map does not permit null keys or values
132	* @throws IllegalArgumentException if some property of the specified key
133	* or value prevents it from being stored in this map
134	*/
135	V replace(K key, V value);
136	}