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/* |
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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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|
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package java.util.concurrent; |
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import java.util.Map; |
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|
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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>This interface is a member of the |
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* <a href="{@docRoot}/../guide/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 <tt>key</tt>, or |
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* <tt>null</tt> if there was no mapping for <tt>key</tt>. |
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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 <tt>key</tt>, |
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* if the implementation supports <tt>null</tt> 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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/** |
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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 associated with the specified key |
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* @return true if the value was removed, false otherwise |
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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 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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*/ |
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boolean remove(Object key, Object value); |
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|
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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 true 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 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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*/ |
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boolean replace(K key, V oldValue, V newValue); |
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|
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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 <tt>key</tt>, or |
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* <tt>null</tt> if there was no mapping for <tt>key</tt>. |
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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 <tt>key</tt>, |
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* if the implementation supports <tt>null</tt> 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 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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*/ |
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V replace(K key, V value); |
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|
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} |
