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>This interface is a member of the
 * <a href="{@docRoot}/../guide/collections/index.html">
 * Java Collections Framework</a>.
 *
 * <p>
 * Memory consistency effects: As with other concurrent collections, state
 * changes to any object made prior to placing it into a <tt>ConcurrentMap</tt> as a key or value
 * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
 * that element is accessed via or removed from the <tt>ConcurrentMap</tt>.
 *
 * @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:	1.28
Committed:	Thu Sep 8 21:58:22 2005 UTC (18 years, 8 months ago) by jsr166
Branch:	MAIN
Changes since 1.27:	+2 -2 lines
Log Message:	whitespace
#	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			* <p>This interface is a member of the
15			* <a href="{@docRoot}/../guide/collections/index.html">
16			* Java Collections Framework</a>.
17	jsr166	1.21	*
18	brian	1.26	* <p>
19	dl	1.27	* Memory consistency effects: As with other concurrent collections, state
20	brian	1.26	* changes to any object made prior to placing it into a <tt>ConcurrentMap</tt> as a key or value
21	jsr166	1.28	* <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
22			* that element is accessed via or removed from the <tt>ConcurrentMap</tt>.
23	brian	1.26	*
24	dl	1.4	* @since 1.5
25			* @author Doug Lea
26	dl	1.13	* @param <K> the type of keys maintained by this map
27	jsr166	1.21	* @param <V> the type of mapped values
28	dl	1.4	*/
29	tim	1.1	public interface ConcurrentMap<K, V> extends Map<K, V> {
30			/**
31			* If the specified key is not already associated
32			* with a value, associate it with the given value.
33			* This is equivalent to
34			* <pre>
35	jsr166	1.21	* if (!map.containsKey(key))
36			* return map.put(key, value);
37	dl	1.5	* else
38	jsr166	1.23	* return map.get(key);</pre>
39	jsr166	1.21	* except that the action is performed atomically.
40			*
41	jsr166	1.24	* @param key key with which the specified value is to be associated
42			* @param value value to be associated with the specified key
43	jsr166	1.25	* @return the previous value associated with the specified key, or
44			* <tt>null</tt> if there was no mapping for the key.
45	jsr166	1.24	* (A <tt>null</tt> return can also indicate that the map
46	jsr166	1.25	* previously associated <tt>null</tt> with the key,
47			* if the implementation supports null values.)
48	jsr166	1.22	* @throws UnsupportedOperationException if the <tt>put</tt> operation
49	jsr166	1.24	* is not supported by this map
50	tim	1.1	* @throws ClassCastException if the class of the specified key or value
51	jsr166	1.24	* prevents it from being stored in this map
52			* @throws NullPointerException if the specified key or value is null,
53			* and this map does not permit null keys or values
54			* @throws IllegalArgumentException if some property of the specified key
55			* or value prevents it from being stored in this map
56	tim	1.1	*
57	dl	1.18	*/
58	dl	1.4	V putIfAbsent(K key, V value);
59	dl	1.6
60			/**
61	jsr166	1.21	* Removes the entry for a key only if currently mapped to a given value.
62			* This is equivalent to
63			* <pre>
64	jsr166	1.24	* if (map.containsKey(key) && map.get(key).equals(value)) {
65	jsr166	1.21	* map.remove(key);
66			* return true;
67	jsr166	1.23	* } else return false;</pre>
68	dl	1.6	* except that the action is performed atomically.
69	jsr166	1.21	*
70	jsr166	1.24	* @param key key with which the specified value is associated
71	jsr166	1.25	* @param value value expected to be associated with the specified key
72			* @return <tt>true</tt> if the value was removed
73	jsr166	1.22	* @throws UnsupportedOperationException if the <tt>remove</tt> operation
74	jsr166	1.24	* is not supported by this map
75	jsr166	1.25	* @throws ClassCastException if the key or value is of an inappropriate
76			* type for this map (optional)
77	jsr166	1.24	* @throws NullPointerException if the specified key or value is null,
78	jsr166	1.25	* and this map does not permit null keys or values (optional)
79	dl	1.6	*/
80	dl	1.7	boolean remove(Object key, Object value);
81	dl	1.14
82			/**
83	jsr166	1.21	* Replaces the entry for a key only if currently mapped to a given value.
84			* This is equivalent to
85			* <pre>
86	jsr166	1.24	* if (map.containsKey(key) && map.get(key).equals(oldValue)) {
87	jsr166	1.21	* map.put(key, newValue);
88			* return true;
89	jsr166	1.23	* } else return false;</pre>
90	dl	1.14	* except that the action is performed atomically.
91	jsr166	1.21	*
92	jsr166	1.24	* @param key key with which the specified value is associated
93			* @param oldValue value expected to be associated with the specified key
94			* @param newValue value to be associated with the specified key
95	jsr166	1.25	* @return <tt>true</tt> if the value was replaced
96	jsr166	1.22	* @throws UnsupportedOperationException if the <tt>put</tt> operation
97	jsr166	1.24	* is not supported by this map
98	jsr166	1.25	* @throws ClassCastException if the class of a specified key or value
99			* prevents it from being stored in this map
100	jsr166	1.24	* @throws NullPointerException if a specified key or value is null,
101			* and this map does not permit null keys or values
102	jsr166	1.25	* @throws IllegalArgumentException if some property of a specified key
103			* or value prevents it from being stored in this map
104	dl	1.14	*/
105			boolean replace(K key, V oldValue, V newValue);
106	dl	1.6
107	dl	1.15	/**
108	jsr166	1.21	* Replaces the entry for a key only if currently mapped to some value.
109			* This is equivalent to
110			* <pre>
111			* if (map.containsKey(key)) {
112			* return map.put(key, value);
113	jsr166	1.23	* } else return null;</pre>
114	dl	1.15	* except that the action is performed atomically.
115	jsr166	1.21	*
116	jsr166	1.24	* @param key key with which the specified value is associated
117			* @param value value to be associated with the specified key
118	jsr166	1.25	* @return the previous value associated with the specified key, or
119			* <tt>null</tt> if there was no mapping for the key.
120	jsr166	1.24	* (A <tt>null</tt> return can also indicate that the map
121	jsr166	1.25	* previously associated <tt>null</tt> with the key,
122			* if the implementation supports null values.)
123	jsr166	1.22	* @throws UnsupportedOperationException if the <tt>put</tt> operation
124	jsr166	1.24	* is not supported by this map
125	jsr166	1.25	* @throws ClassCastException if the class of the specified key or value
126			* prevents it from being stored in this map
127	jsr166	1.24	* @throws NullPointerException if the specified key or value is null,
128			* and this map does not permit null keys or values
129	jsr166	1.25	* @throws IllegalArgumentException if some property of the specified key
130			* or value prevents it from being stored in this map
131	dl	1.15	*/
132	dl	1.16	V replace(K key, V value);
133	tim	1.1	}