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- Type Parameters:
K
- the type of keys maintained by this mapV
- the type of mapped values
- All Superinterfaces:
- Map<K,V>
- All Known Subinterfaces:
- ConcurrentNavigableMap<K,V>
- All Known Implementing Classes:
- ConcurrentHashMap, ConcurrentSkipListMap
public interface ConcurrentMap<K,V> extends Map<K,V>
AMap
providing additional atomic putIfAbsent, remove, and replace methods.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 theConcurrentMap
in another thread.This interface is a member of the Java Collections Framework.
- Since:
- 1.5
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Method Summary
Methods Modifier and Type Method and Description 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.
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Method Detail
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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 toif (!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 associatedvalue
- 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 mapClassCastException
- if the class of the specified key or value prevents it from being stored in this mapNullPointerException
- if the specified key or value is null, and this map does not permit null keys or valuesIllegalArgumentException
- if some property of the specified key or value prevents it from being stored in this map
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remove
boolean remove(Object key, Object value)
Removes the entry for a key only if currently mapped to a given value. This is equivalent toif (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 associatedvalue
- 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 mapClassCastException
- 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)
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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 toif (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 associatedoldValue
- value expected to be associated with the specified keynewValue
- 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 mapClassCastException
- if the class of a specified key or value prevents it from being stored in this mapNullPointerException
- if a specified key or value is null, and this map does not permit null keys or valuesIllegalArgumentException
- if some property of a specified key or value prevents it from being stored in this map
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replace
V replace(K key, V value)
Replaces the entry for a key only if currently mapped to some value. This is equivalent toif (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 associatedvalue
- 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 mapClassCastException
- if the class of the specified key or value prevents it from being stored in this mapNullPointerException
- if the specified key or value is null, and this map does not permit null keys or valuesIllegalArgumentException
- if some property of the specified key or value prevents it from being stored in this map
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