public interface ConcurrentMap
extends java.util.Map
Map
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
the ConcurrentMap
in another thread.
This interface is a member of the Java Collections Framework.
Modifier and Type | Method and Description |
---|---|
java.lang.Object |
putIfAbsent(java.lang.Object key,
java.lang.Object value)
If the specified key is not already associated
with a value, associate it with the given value.
|
boolean |
remove(java.lang.Object key,
java.lang.Object value)
Removes the entry for a key only if currently mapped to a given value.
|
java.lang.Object |
replace(java.lang.Object key,
java.lang.Object value)
Replaces the entry for a key only if currently mapped to some value.
|
boolean |
replace(java.lang.Object key,
java.lang.Object oldValue,
java.lang.Object newValue)
Replaces the entry for a key only if currently mapped to a given value.
|
java.lang.Object putIfAbsent(java.lang.Object key, java.lang.Object value)
if (!map.containsKey(key)) return map.put(key, value); else return map.get(key);except that the action is performed atomically.
key
- key with which the specified value is to be associatedvalue
- value to be associated with the specified keyjava.lang.UnsupportedOperationException
- if the put operation
is not supported by this mapjava.lang.ClassCastException
- if the class of the specified key or value
prevents it from being stored in this mapjava.lang.NullPointerException
- if the specified key or value is null,
and this map does not permit null keys or valuesjava.lang.IllegalArgumentException
- if some property of the specified key
or value prevents it from being stored in this mapboolean remove(java.lang.Object key, java.lang.Object value)
if (map.containsKey(key) && map.get(key).equals(value)) { map.remove(key); return true; } else return false;except that the action is performed atomically.
key
- key with which the specified value is associatedvalue
- value expected to be associated with the specified keyjava.lang.UnsupportedOperationException
- if the remove operation
is not supported by this mapjava.lang.ClassCastException
- if the key or value is of an inappropriate
type for this map (optional)java.lang.NullPointerException
- if the specified key or value is null,
and this map does not permit null keys or values (optional)boolean replace(java.lang.Object key, java.lang.Object oldValue, java.lang.Object newValue)
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.
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 keyjava.lang.UnsupportedOperationException
- if the put operation
is not supported by this mapjava.lang.ClassCastException
- if the class of a specified key or value
prevents it from being stored in this mapjava.lang.NullPointerException
- if a specified key or value is null,
and this map does not permit null keys or valuesjava.lang.IllegalArgumentException
- if some property of a specified key
or value prevents it from being stored in this mapjava.lang.Object replace(java.lang.Object key, java.lang.Object value)
if (map.containsKey(key)) { return map.put(key, value); } else return null;except that the action is performed atomically.
key
- key with which the specified value is associatedvalue
- value to be associated with the specified keyjava.lang.UnsupportedOperationException
- if the put operation
is not supported by this mapjava.lang.ClassCastException
- if the class of the specified key or value
prevents it from being stored in this mapjava.lang.NullPointerException
- if the specified key or value is null,
and this map does not permit null keys or valuesjava.lang.IllegalArgumentException
- if some property of the specified key
or value prevents it from being stored in this map