ConcurrentMap (Java Platform SE 6)

Memory consistency effects: As with other concurrent collections, actions in a thread prior to placing an object into a ConcurrentMap as a key or value happen-before actions subsequent to the access or removal of that object from the ConcurrentMap in another thread.

This interface is a member of the Java Collections Framework.

Since:: 1.5

Nested Class Summary

Nested classes/interfaces inherited from interface java.util.Map
`Map.Entry<K,V>`

Method Summary
`V`	`putIfAbsent(K key, V value)` If the specified key is not already associated with a value, associate it with the given value.
`boolean`	`remove(Object key, Object value)` Removes the entry for a key only if currently mapped to a given value.
`V`	`replace(K key, V value)` Replaces the entry for a key only if currently mapped to some value.
`boolean`	`replace(K key, V oldValue, V newValue)` Replaces the entry for a key only if currently mapped to a given value.

Methods inherited from interface java.util.Map
`clear, containsKey, containsValue, entrySet, equals, get, hashCode, isEmpty, keySet, put, putAll, remove, size, values`

Method Detail

putIfAbsent

V putIfAbsent(K key,
 V value)

If the specified key is not already associated with a value, associate it with the given value. This is equivalent to

 if (!map.containsKey(key))
 return map.put(key, value);
 else
 return map.get(key);

except that the action is performed atomically.

Parameters:: key - key with which the specified value is to be associated; value - value to be associated with the specified key
Returns:: the previous value associated with the specified key, or null if there was no mapping for the key. (A null return can also indicate that the map previously associated null with the key, if the implementation supports null values.)
Throws:: UnsupportedOperationException - if the put operation is not supported by this map; ClassCastException - if the class of the specified key or value prevents it from being stored in this map; NullPointerException - if the specified key or value is null, and this map does not permit null keys or values; IllegalArgumentException - if some property of the specified key or value prevents it from being stored in this map

remove

boolean remove(Object key,
 Object value)

Removes the entry for a key only if currently mapped to a given value. This is equivalent to

 if (map.containsKey(key) && map.get(key).equals(value)) {
 map.remove(key);
 return true;
 } else return false;

except that the action is performed atomically.

Parameters:: key - key with which the specified value is associated; value - value expected to be associated with the specified key
Returns:: true if the value was removed
Throws:: UnsupportedOperationException - if the remove operation is not supported by this map; ClassCastException - if the key or value is of an inappropriate type for this map (optional); NullPointerException - if the specified key or value is null, and this map does not permit null keys or values (optional)

replace

boolean replace(K key,
 V oldValue,
 V newValue)

Replaces the entry for a key only if currently mapped to a given value. This is equivalent to

 if (map.containsKey(key) && map.get(key).equals(oldValue)) {
 map.put(key, newValue);
 return true;
 } else return false;

except that the action is performed atomically.

Parameters:: key - key with which the specified value is associated; oldValue - value expected to be associated with the specified key; newValue - value to be associated with the specified key
Returns:: true if the value was replaced
Throws:: UnsupportedOperationException - if the put operation is not supported by this map; ClassCastException - if the class of a specified key or value prevents it from being stored in this map; NullPointerException - if a specified key or value is null, and this map does not permit null keys or values; IllegalArgumentException - if some property of a specified key or value prevents it from being stored in this map

replace

V replace(K key,
 V value)

Replaces the entry for a key only if currently mapped to some value. This is equivalent to

 if (map.containsKey(key)) {
 return map.put(key, value);
 } else return null;

except that the action is performed atomically.

Parameters:: key - key with which the specified value is associated; value - value to be associated with the specified key
Returns:: the previous value associated with the specified key, or null if there was no mapping for the key. (A null return can also indicate that the map previously associated null with the key, if the implementation supports null values.)
Throws:: UnsupportedOperationException - if the put operation is not supported by this map; ClassCastException - if the class of the specified key or value prevents it from being stored in this map; NullPointerException - if the specified key or value is null, and this map does not permit null keys or values; IllegalArgumentException - if some property of the specified key or value prevents it from being stored in this map

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For further API reference and developer documentation, see Java SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

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java.util.concurrent Interface ConcurrentMap<K,V>

putIfAbsent

remove

replace

replace

java.util.concurrent
Interface ConcurrentMap<K,V>