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/licenses/publicdomain
 */

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 (optional)
     * @throws NullPointerException if the specified key or value is null,
     *         and this map does not permit null keys or values (optional)
     */
    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:	1.30
Committed:	Sun May 28 23:36:29 2006 UTC (18 years ago) by jsr166
Branch:	MAIN
Changes since 1.29:	+1 -1 lines
Log Message:	Location of Collections Guide has changed
#	User	Rev	Content
1	dl	1.2	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3	dl	1.17	* Expert Group and released to the public domain, as explained at
4			* http://creativecommons.org/licenses/publicdomain
5	dl	1.2	*/
6
7	tim	1.1	package java.util.concurrent;
8			import java.util.Map;
9
10			/**
11	dl	1.11	* A {@link java.util.Map} providing additional atomic
12	dl	1.14	* <tt>putIfAbsent</tt>, <tt>remove</tt>, and <tt>replace</tt> methods.
13	dl	1.19	*
14	jsr166	1.29	* <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	dl	1.19	* <p>This interface is a member of the
22	jsr166	1.30	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
23	dl	1.19	* Java Collections Framework</a>.
24	jsr166	1.21	*
25	dl	1.4	* @since 1.5
26			* @author Doug Lea
27	dl	1.13	* @param <K> the type of keys maintained by this map
28	jsr166	1.21	* @param <V> the type of mapped values
29	dl	1.4	*/
30	tim	1.1	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	jsr166	1.21	* if (!map.containsKey(key))
37			* return map.put(key, value);
38	dl	1.5	* else
39	jsr166	1.23	* return map.get(key);</pre>
40	jsr166	1.21	* except that the action is performed atomically.
41			*
42	jsr166	1.24	* @param key key with which the specified value is to be associated
43			* @param value value to be associated with the specified key
44	jsr166	1.25	* @return the previous value associated with the specified key, or
45			* <tt>null</tt> if there was no mapping for the key.
46	jsr166	1.24	* (A <tt>null</tt> return can also indicate that the map
47	jsr166	1.25	* previously associated <tt>null</tt> with the key,
48			* if the implementation supports null values.)
49	jsr166	1.22	* @throws UnsupportedOperationException if the <tt>put</tt> operation
50	jsr166	1.24	* is not supported by this map
51	tim	1.1	* @throws ClassCastException if the class of the specified key or value
52	jsr166	1.24	* 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	tim	1.1	*
58	dl	1.18	*/
59	dl	1.4	V putIfAbsent(K key, V value);
60	dl	1.6
61			/**
62	jsr166	1.21	* Removes the entry for a key only if currently mapped to a given value.
63			* This is equivalent to
64			* <pre>
65	jsr166	1.24	* if (map.containsKey(key) && map.get(key).equals(value)) {
66	jsr166	1.21	* map.remove(key);
67			* return true;
68	jsr166	1.23	* } else return false;</pre>
69	dl	1.6	* except that the action is performed atomically.
70	jsr166	1.21	*
71	jsr166	1.24	* @param key key with which the specified value is associated
72	jsr166	1.25	* @param value value expected to be associated with the specified key
73			* @return <tt>true</tt> if the value was removed
74	jsr166	1.22	* @throws UnsupportedOperationException if the <tt>remove</tt> operation
75	jsr166	1.24	* is not supported by this map
76	jsr166	1.25	* @throws ClassCastException if the key or value is of an inappropriate
77			* type for this map (optional)
78	jsr166	1.24	* @throws NullPointerException if the specified key or value is null,
79	jsr166	1.25	* and this map does not permit null keys or values (optional)
80	dl	1.6	*/
81	dl	1.7	boolean remove(Object key, Object value);
82	dl	1.14
83			/**
84	jsr166	1.21	* Replaces the entry for a key only if currently mapped to a given value.
85			* This is equivalent to
86			* <pre>
87	jsr166	1.24	* if (map.containsKey(key) && map.get(key).equals(oldValue)) {
88	jsr166	1.21	* map.put(key, newValue);
89			* return true;
90	jsr166	1.23	* } else return false;</pre>
91	dl	1.14	* except that the action is performed atomically.
92	jsr166	1.21	*
93	jsr166	1.24	* @param key key with which the specified value is associated
94			* @param oldValue value expected to be associated with the specified key
95			* @param newValue value to be associated with the specified key
96	jsr166	1.25	* @return <tt>true</tt> if the value was replaced
97	jsr166	1.22	* @throws UnsupportedOperationException if the <tt>put</tt> operation
98	jsr166	1.24	* is not supported by this map
99	jsr166	1.25	* @throws ClassCastException if the class of a specified key or value
100			* prevents it from being stored in this map
101	jsr166	1.24	* @throws NullPointerException if a specified key or value is null,
102			* and this map does not permit null keys or values
103	jsr166	1.25	* @throws IllegalArgumentException if some property of a specified key
104			* or value prevents it from being stored in this map
105	dl	1.14	*/
106			boolean replace(K key, V oldValue, V newValue);
107	dl	1.6
108	dl	1.15	/**
109	jsr166	1.21	* Replaces the entry for a key only if currently mapped to some value.
110			* This is equivalent to
111			* <pre>
112			* if (map.containsKey(key)) {
113			* return map.put(key, value);
114	jsr166	1.23	* } else return null;</pre>
115	dl	1.15	* except that the action is performed atomically.
116	jsr166	1.21	*
117	jsr166	1.24	* @param key key with which the specified value is associated
118			* @param value value to be associated with the specified key
119	jsr166	1.25	* @return the previous value associated with the specified key, or
120			* <tt>null</tt> if there was no mapping for the key.
121	jsr166	1.24	* (A <tt>null</tt> return can also indicate that the map
122	jsr166	1.25	* previously associated <tt>null</tt> with the key,
123			* if the implementation supports null values.)
124	jsr166	1.22	* @throws UnsupportedOperationException if the <tt>put</tt> operation
125	jsr166	1.24	* is not supported by this map
126	jsr166	1.25	* @throws ClassCastException if the class of the specified key or value
127			* prevents it from being stored in this map
128	jsr166	1.24	* @throws NullPointerException if the specified key or value is null,
129			* and this map does not permit null keys or values
130	jsr166	1.25	* @throws IllegalArgumentException if some property of the specified key
131			* or value prevents it from being stored in this map
132	dl	1.15	*/
133	dl	1.16	V replace(K key, V value);
134	tim	1.1	}