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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. Use, modify, and |
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* redistribute this code in any way without acknowledgement. |
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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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* @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); |
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* </pre> |
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* Except that the action is performed atomically. |
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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 previous value associated with specified key, or <tt>null</tt> |
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* if there was no mapping for key. A <tt>null</tt> return can |
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* also indicate that the map previously associated <tt>null</tt> |
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* with the specified key, if the implementation supports |
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* <tt>null</tt> values. |
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* |
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* @throws UnsupportedOperationException if the <tt>put</tt> operation is |
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* 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 IllegalArgumentException if some aspect of this key or value |
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* prevents it from being stored in this map. |
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* @throws NullPointerException if this map does not permit <tt>null</tt> |
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* keys or values, and the specified key or value is |
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* <tt>null</tt>. |
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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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* Remove entry for key only if currently mapped to given value. |
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* Acts as |
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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; |
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* </pre> |
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* except that the action is performed atomically. |
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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 |
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* @throws NullPointerException if this map does not permit <tt>null</tt> |
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* keys or values, and the specified key or value is |
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* <tt>null</tt>. |
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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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/** |
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* Replace entry for key only if currently mapped to given value. |
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* Acts as |
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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; |
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* </pre> |
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* except that the action is performed atomically. |
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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 NullPointerException if this map does not permit <tt>null</tt> |
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* keys or values, and the specified key or value is |
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* <tt>null</tt>. |
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*/ |
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boolean replace(K key, V oldValue, V newValue); |
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|
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} |
