K
- the type of the map entry keysV
- the type of the map entry valuespublic interface ConcurrentMap<K,V> extends Map<K,V>
Modifier and Type | Field and Description |
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static Object |
LOCK_ALL
Special key value indicating an intent to lock the entire map.
|
Modifier and Type | Method and Description |
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void |
clear()
Removes all mappings from this map.
|
boolean |
containsKey(Object key)
Returns true if this map contains a mapping for the specified key.
|
boolean |
containsValue(Object value)
Returns true if this map maps one or more keys to the specified value.
|
V |
get(Object key)
Returns the value to which this map maps the specified key.
|
boolean |
isEmpty()
Returns true if this map contains no key-value mappings.
|
boolean |
lock(Object oKey)
Attempt to lock the specified item and return immediately.
|
boolean |
lock(Object oKey, long cWait)
Attempt to lock the specified item within the specified period of time.
|
V |
put(K key, V value)
Associates the specified value with the specified key in this map (optional operation).
|
void |
putAll(Map<? extends K,? extends V> map)
Copies all of the mappings from the specified map to this map (optional operation).
|
V |
remove(Object key)
Removes the mapping for this key from this map if present (optional operation).
|
int |
size()
Returns the number of key-value mappings in this map.
|
boolean |
unlock(Object oKey)
Unlock the specified item.
|
compute, computeIfAbsent, computeIfPresent, entrySet, equals, forEach, getOrDefault, hashCode, keySet, merge, putIfAbsent, remove, replace, replace, replaceAll, values
static final Object LOCK_ALL
boolean lock(Object oKey, long cWait)
The item doesn't have to exist to be locked. While the item is locked there is known to be a lock holder which has an exclusive right to modify (calling put and remove methods) that item.
Lock holder is an abstract concept that depends on the ConcurrentMap implementation. For example, holder could be a cluster member or a thread (or both).
Locking strategy may vary for concrete implementations as well. Lock could have an expiration time (this lock is sometimes called a "lease") or be held indefinitely (until the lock holder terminates).
Some implementations may allow the entire map to be locked. If the map is locked in such a way, then only a lock holder is allowed to perform any of the "put" or "remove" operations. Pass the special constant LOCK_ALL
as the oKey parameter to indicate the map lock.
oKey
- key being lockedcWait
- the number of milliseconds to continue trying to obtain a lock; pass zero to return immediately; pass -1 to block the calling thread until the lock could be obtainedboolean lock(Object oKey)
This method behaves exactly as if it simply performs the call lock(oKey, 0).
oKey
- key being lockedboolean unlock(Object oKey)
oKey
- key being unlockedint size()
boolean isEmpty()
boolean containsKey(Object key)
containsKey
in interface Map<K,V>
key
- key whose presence in this map is to be testedClassCastException
- if the key is of an inappropriate type for this mapNullPointerException
- if the key is null and this map does not not permit null keysboolean containsValue(Object value)
containsValue
in interface Map<K,V>
value
- value whose presence in this map is to be testedV get(Object key)
get
in interface Map<K,V>
key
- key whose associated value is to be returnedClassCastException
- if the key is of an inappropriate type for this mapNullPointerException
- key is null and this map does not not permit null keyscontainsKey(Object)
V put(K key, V value)
Some implementations will attempt to obtain a lock for the key (if necessary) before proceeding with the put operation. For such implementations, the specified item has to be either already locked or able to be locked for this operation to succeed.
put
in interface Map<K,V>
key
- key with which the specified value is to be associatedvalue
- value to be associated with the specified keyIllegalArgumentException
- if the value cannot be stored in the map (i.e. not serializable)ConcurrentModificationException
- if the lock could not be successfully obtained for the specified keyClassCastException
- if the class of the specified key or value prevents it from being stored in this mapNullPointerException
- this map does not permit null keys or values, and the specified key or value is nullV remove(Object key)
Some implementations will attempt to obtain a lock for the key (if necessary) before proceeding with the remove operation. For such implementations, the specified item has to be either already locked or able to be locked for this operation to succeed.
remove
in interface Map<K,V>
key
- key whose mapping is to be removed from the mapConcurrentModificationException
- if the lock could not be successfully obtained for the specified keyvoid putAll(Map<? extends K,? extends V> map)
putAll
in interface Map<K,V>
map
- Mappings to be stored in this mapClassCastException
- if the class of a key or value in the specified map prevents it from being stored in this mapConcurrentModificationException
- if the lock could not be successfully obtained for some keyNullPointerException
- this map does not permit null keys or values, and the specified key or value is nullvoid clear()
Some implementations will attempt to lock the entire map (if necessary) before proceeding with the clear operation. For such implementations, the entire map has to be either already locked or able to be locked for this operation to succeed.
clear
in interface Map<K,V>
ConcurrentModificationException
- if a lock could not be successfully obtained for some key