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Préférences
Moteurs de recherche
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JavaTM 2 Platform Std. Ed. v1.6.0
java.util.concurrent
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Nested Class Summary |
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Nested classes/interfaces inherited from class java.util.AbstractMap |
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AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V> |
Nested classes/interfaces inherited from interface java.util.Map |
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Map.Entry<K,V> |
Constructor Summary | |
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ConcurrentHashMap()
Creates a new, empty map with a default initial capacity (16), load factor (0.75) and concurrencyLevel (16). |
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ConcurrentHashMap(int initialCapacity)
Creates a new, empty map with the specified initial capacity, and with default load factor (0.75) and concurrencyLevel (16). |
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ConcurrentHashMap(int initialCapacity,
float loadFactor)
Creates a new, empty map with the specified initial capacity and load factor and with the default concurrencyLevel (16). |
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ConcurrentHashMap(int initialCapacity,
float loadFactor,
int concurrencyLevel)
Creates a new, empty map with the specified initial capacity, load factor and concurrency level. |
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ConcurrentHashMap(Map<? extends K,? extends V> m)
Creates a new map with the same mappings as the given map. |
Method Summary | |
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void |
clear()
Removes all of the mappings from this map. |
boolean |
contains(Object value)
Legacy method testing if some key maps into the specified value in this table. |
boolean |
containsKey(Object key)
Tests if the specified object is a key in this table. |
boolean |
containsValue(Object value)
Returns true if this map maps one or more keys to the specified value. |
Enumeration<V> |
elements()
Returns an enumeration of the values in this table. |
Set<Map.Entry<K,V>> |
entrySet()
Returns a Set view of the mappings contained in this map. |
V |
get(Object key)
Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key. |
boolean |
isEmpty()
Returns true if this map contains no key-value mappings. |
Enumeration<K> |
keys()
Returns an enumeration of the keys in this table. |
Set<K> |
keySet()
Returns a Set view of the keys contained in this map. |
V |
put(K key,
V value)
Maps the specified key to the specified value in this table. |
void |
putAll(Map<? extends K,? extends V> m)
Copies all of the mappings from the specified map to this one. |
V |
putIfAbsent(K key,
V value)
If the specified key is not already associated with a value, associate it with the given value. |
V |
remove(Object key)
Removes the key (and its corresponding value) from this map. |
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. |
int |
size()
Returns the number of key-value mappings in this map. |
Collection<V> |
values()
Returns a Collection view of the values contained in this map. |
Methods inherited from class java.util.AbstractMap |
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clone, equals, hashCode, toString |
Methods inherited from class java.lang.Object |
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finalize, getClass, notify, notifyAll, wait, wait, wait |
Methods inherited from interface java.util.Map |
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equals, hashCode |
Constructor Detail |
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public ConcurrentHashMap(int initialCapacity, float loadFactor, int concurrencyLevel)
initialCapacity
- the initial capacity. The implementation
performs internal sizing to accommodate this many elements.loadFactor
- the load factor threshold, used to control resizing.
Resizing may be performed when the average number of elements per
bin exceeds this threshold.concurrencyLevel
- the estimated number of concurrently
updating threads. The implementation performs internal sizing
to try to accommodate this many threads.
IllegalArgumentException
- if the initial capacity is
negative or the load factor or concurrencyLevel are
nonpositive.public ConcurrentHashMap(int initialCapacity, float loadFactor)
initialCapacity
- The implementation performs internal
sizing to accommodate this many elements.loadFactor
- the load factor threshold, used to control resizing.
Resizing may be performed when the average number of elements per
bin exceeds this threshold.
IllegalArgumentException
- if the initial capacity of
elements is negative or the load factor is nonpositivepublic ConcurrentHashMap(int initialCapacity)
initialCapacity
- the initial capacity. The implementation
performs internal sizing to accommodate this many elements.
IllegalArgumentException
- if the initial capacity of
elements is negative.public ConcurrentHashMap()
public ConcurrentHashMap(Map<? extends K,? extends V> m)
m
- the mapMethod Detail |
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public boolean isEmpty()
public int size()
public V get(Object key)
null
if this map contains no mapping for the key.
More formally, if this map contains a mapping from a key
k
to a value v
such that key.equals(k)
,
then this method returns v
; otherwise it returns
null
. (There can be at most one such mapping.)
key
- the key whose associated value is to be returned
null
if this map contains no mapping for the key
NullPointerException
- if the specified key is nullpublic boolean containsKey(Object key)
containsKey
in interface Map<K,V>
containsKey
in class AbstractMap<K,V>
key
- possible key
NullPointerException
- if the specified key is nullpublic boolean containsValue(Object value)
containsValue
in interface Map<K,V>
containsValue
in class AbstractMap<K,V>
value
- value whose presence in this map is to be tested
NullPointerException
- if the specified value is nullpublic boolean contains(Object value)
containsValue(java.lang.Object)
, and exists solely to ensure
full compatibility with class Hashtable
,
which supported this method prior to introduction of the
Java Collections framework.
value
- a value to search for
NullPointerException
- if the specified value is nullpublic V put(K key, V value)
The value can be retrieved by calling the get method with a key that is equal to the original key.
key
- key with which the specified value is to be associatedvalue
- value to be associated with the specified key
NullPointerException
- if the specified key or value is nullpublic V putIfAbsent(K key, V value)
if (!map.containsKey(key)) return map.put(key, value); else return map.get(key);except that the action is performed atomically.
putIfAbsent
in interface ConcurrentMap<K,V>
key
- key with which the specified value is to be associatedvalue
- value to be associated with the specified key
NullPointerException
- if the specified key or value is nullpublic void putAll(Map<? extends K,? extends V> m)
m
- mappings to be stored in this mappublic V remove(Object key)
key
- the key that needs to be removed
NullPointerException
- if the specified key is nullpublic boolean remove(Object key, 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.
remove
in interface ConcurrentMap<K,V>
key
- key with which the specified value is associatedvalue
- value expected to be associated with the specified key
NullPointerException
- if the specified key is nullpublic boolean replace(K key, V oldValue, V 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.
replace
in interface ConcurrentMap<K,V>
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
NullPointerException
- if any of the arguments are nullpublic V replace(K key, V value)
if (map.containsKey(key)) { return map.put(key, value); } else return null;except that the action is performed atomically.
replace
in interface ConcurrentMap<K,V>
key
- key with which the specified value is associatedvalue
- value to be associated with the specified key
NullPointerException
- if the specified key or value is nullpublic void clear()
public Set<K> keySet()
Set
view of the keys contained in this map.
The set is backed by the map, so changes to the map are
reflected in the set, and vice-versa. The set supports element
removal, which removes the corresponding mapping from this map,
via the Iterator.remove, Set.remove,
removeAll, retainAll, and clear
operations. It does not support the add or
addAll operations.
The view's iterator is a "weakly consistent" iterator
that will never throw ConcurrentModificationException
,
and guarantees to traverse elements as they existed upon
construction of the iterator, and may (but is not guaranteed to)
reflect any modifications subsequent to construction.
public Collection<V> values()
Collection
view of the values contained in this map.
The collection is backed by the map, so changes to the map are
reflected in the collection, and vice-versa. The collection
supports element removal, which removes the corresponding
mapping from this map, via the Iterator.remove,
Collection.remove, removeAll,
retainAll, and clear operations. It does not
support the add or addAll operations.
The view's iterator is a "weakly consistent" iterator
that will never throw ConcurrentModificationException
,
and guarantees to traverse elements as they existed upon
construction of the iterator, and may (but is not guaranteed to)
reflect any modifications subsequent to construction.
public Set<Map.Entry<K,V>> entrySet()
Set
view of the mappings contained in this map.
The set is backed by the map, so changes to the map are
reflected in the set, and vice-versa. The set supports element
removal, which removes the corresponding mapping from the map,
via the Iterator.remove, Set.remove,
removeAll, retainAll, and clear
operations. It does not support the add or
addAll operations.
The view's iterator is a "weakly consistent" iterator
that will never throw ConcurrentModificationException
,
and guarantees to traverse elements as they existed upon
construction of the iterator, and may (but is not guaranteed to)
reflect any modifications subsequent to construction.
public Enumeration<K> keys()
keySet()
public Enumeration<V> elements()
values()