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jeremybenn |
/*
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* Written by Doug Lea with assistance from members of JCP JSR-166
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* Expert Group and released to the public domain, as explained at
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* http://creativecommons.org/licenses/publicdomain
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*/
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package java.util.concurrent;
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import java.util.Map;
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/**
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* A {@link java.util.Map} providing additional atomic
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* <tt>putIfAbsent</tt>, <tt>remove</tt>, and <tt>replace</tt> methods.
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*
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* <p>Memory consistency effects: As with other concurrent
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* collections, actions in a thread prior to placing an object into a
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* {@code ConcurrentMap} as a key or value
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* <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
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* actions subsequent to the access or removal of that object from
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* the {@code ConcurrentMap} in another thread.
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*
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* <p>This interface is a member of the
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* <a href="{@docRoot}/../technotes/guides/collections/index.html">
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* Java Collections Framework</a>.
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*
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* @since 1.5
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* @author Doug Lea
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* @param <K> the type of keys maintained by this map
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* @param <V> the type of mapped values
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*/
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public interface ConcurrentMap<K, V> extends Map<K, V> {
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/**
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* If the specified key is not already associated
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* with a value, associate it with the given value.
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* This is equivalent to
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* <pre>
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* if (!map.containsKey(key))
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* return map.put(key, value);
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* else
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* return map.get(key);</pre>
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* except that the action is performed atomically.
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*
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* @param key key with which the specified value is to be associated
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* @param value value to be associated with the specified key
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* @return the previous value associated with the specified key, or
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* <tt>null</tt> if there was no mapping for the key.
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* (A <tt>null</tt> return can also indicate that the map
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* previously associated <tt>null</tt> with the key,
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* if the implementation supports null values.)
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* @throws UnsupportedOperationException if the <tt>put</tt> operation
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* is not supported by this map
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* @throws ClassCastException if the class of the specified key or value
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* prevents it from being stored in this map
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* @throws NullPointerException if the specified key or value is null,
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* and this map does not permit null keys or values
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* @throws IllegalArgumentException if some property of the specified key
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* or value prevents it from being stored in this map
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*
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*/
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V putIfAbsent(K key, V value);
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/**
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* Removes the entry for a key only if currently mapped to a given value.
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* This is equivalent to
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* <pre>
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* if (map.containsKey(key) && map.get(key).equals(value)) {
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* map.remove(key);
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* return true;
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* } else return false;</pre>
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* except that the action is performed atomically.
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*
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* @param key key with which the specified value is associated
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* @param value value expected to be associated with the specified key
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* @return <tt>true</tt> if the value was removed
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* @throws UnsupportedOperationException if the <tt>remove</tt> operation
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* is not supported by this map
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* @throws ClassCastException if the key or value is of an inappropriate
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* type for this map (optional)
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* @throws NullPointerException if the specified key or value is null,
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* and this map does not permit null keys or values (optional)
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*/
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boolean remove(Object key, Object value);
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/**
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* Replaces the entry for a key only if currently mapped to a given value.
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* This is equivalent to
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* <pre>
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* if (map.containsKey(key) && map.get(key).equals(oldValue)) {
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* map.put(key, newValue);
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* return true;
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* } else return false;</pre>
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* except that the action is performed atomically.
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*
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* @param key key with which the specified value is associated
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* @param oldValue value expected to be associated with the specified key
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* @param newValue value to be associated with the specified key
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* @return <tt>true</tt> if the value was replaced
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* @throws UnsupportedOperationException if the <tt>put</tt> operation
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* is not supported by this map
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* @throws ClassCastException if the class of a specified key or value
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* prevents it from being stored in this map
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* @throws NullPointerException if a specified key or value is null,
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* and this map does not permit null keys or values
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* @throws IllegalArgumentException if some property of a specified key
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* or value prevents it from being stored in this map
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*/
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boolean replace(K key, V oldValue, V newValue);
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/**
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* Replaces the entry for a key only if currently mapped to some value.
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* This is equivalent to
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* <pre>
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* if (map.containsKey(key)) {
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* return map.put(key, value);
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* } else return null;</pre>
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* except that the action is performed atomically.
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*
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* @param key key with which the specified value is associated
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* @param value value to be associated with the specified key
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* @return the previous value associated with the specified key, or
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* <tt>null</tt> if there was no mapping for the key.
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* (A <tt>null</tt> return can also indicate that the map
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* previously associated <tt>null</tt> with the key,
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* if the implementation supports null values.)
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* @throws UnsupportedOperationException if the <tt>put</tt> operation
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* is not supported by this map
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* @throws ClassCastException if the class of the specified key or value
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* prevents it from being stored in this map
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* @throws NullPointerException if the specified key or value is null,
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* and this map does not permit null keys or values
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* @throws IllegalArgumentException if some property of the specified key
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* or value prevents it from being stored in this map
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*/
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V replace(K key, V value);
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}
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