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Préférences
Moteurs de recherche
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JavaTM 2 Platform Std. Ed. v1.6.0
java.util
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Nested Class Summary | |
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static interface |
Map.Entry<K,V>
A map entry (key-value pair). |
Method Summary | |
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void |
clear()
Removes all of the mappings from this map (optional operation). |
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. |
Set<Map.Entry<K,V>> |
entrySet()
Returns a Set view of the mappings contained in this map. |
boolean |
equals(Object o)
Compares the specified object with this map for equality. |
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. |
int |
hashCode()
Returns the hash code value for this map. |
boolean |
isEmpty()
Returns true if this map contains no key-value mappings. |
Set<K> |
keySet()
Returns a Set view of the keys contained in this map. |
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> m)
Copies all of the mappings from the specified map to this map (optional operation). |
V |
remove(Object key)
Removes the mapping for a key from this map if it is present (optional operation). |
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. |
Method Detail |
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int size()
boolean isEmpty()
boolean containsKey(Object key)
key
- key whose presence in this map is to be tested
ClassCastException
- if the key is of an inappropriate type for
this map (optional)
NullPointerException
- if the specified key is null and this map
does not permit null keys (optional)boolean containsValue(Object value)
value
- value whose presence in this map is to be tested
ClassCastException
- if the value is of an inappropriate type for
this map (optional)
NullPointerException
- if the specified value is null and this
map does not permit null values (optional)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==null ? k==null :
key.equals(k))
, then this method returns v
; otherwise
it returns null
. (There can be at most one such mapping.)
If this map permits null values, then a return value of
null
does not necessarily indicate that the map
contains no mapping for the key; it's also possible that the map
explicitly maps the key to null
. The containsKey
operation may be used to distinguish these two cases.
key
- the key whose associated value is to be returned
null
if this map contains no mapping for the key
ClassCastException
- if the key is of an inappropriate type for
this map (optional)
NullPointerException
- if the specified key is null and this map
does not permit null keys (optional)V put(K key, V value)
m.containsKey(k)
would return
true.)
key
- key with which the specified value is to be associatedvalue
- value to be associated with the specified key
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 mapV remove(Object key)
(key==null ? k==null : key.equals(k))
, that mapping
is removed. (The map can contain at most one such mapping.)
Returns the value to which this map previously associated the key, or null if the map contained no mapping for the key.
If this map permits null values, then a return value of null does not necessarily indicate that the map contained no mapping for the key; it's also possible that the map explicitly mapped the key to null.
The map will not contain a mapping for the specified key once the call returns.
key
- key whose mapping is to be removed from the map
UnsupportedOperationException
- if the remove operation
is not supported by this map
ClassCastException
- if the key is of an inappropriate type for
this map (optional)
NullPointerException
- if the specified key is null and this
map does not permit null keys (optional)void putAll(Map<? extends K,? extends V> m)
put(k, v)
on this map once
for each mapping from key k to value v in the
specified map. The behavior of this operation is undefined if the
specified map is modified while the operation is in progress.
m
- mappings to be stored in this map
UnsupportedOperationException
- if the putAll operation
is not supported by this map
ClassCastException
- if the class of a key or value in the
specified map prevents it from being stored in this map
NullPointerException
- if the specified map is null, or if
this map does not permit null keys or values, and the
specified map contains null keys or values
IllegalArgumentException
- if some property of a key or value in
the specified map prevents it from being stored in this mapvoid clear()
UnsupportedOperationException
- if the clear operation
is not supported by this mapSet<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. If the map is modified
while an iteration over the set is in progress (except through
the iterator's own remove operation), the results of
the iteration are undefined. 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.
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. If the map is
modified while an iteration over the collection is in progress
(except through the iterator's own remove operation),
the results of the iteration are undefined. The collection
supports element removal, which removes the corresponding
mapping from the map, via the Iterator.remove,
Collection.remove, removeAll,
retainAll and clear operations. It does not
support the add or addAll operations.
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. If the map is modified
while an iteration over the set is in progress (except through
the iterator's own remove operation, or through the
setValue operation on a map entry returned by the
iterator) the results of the iteration are undefined. 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.
boolean equals(Object o)
o
- object to be compared for equality with this map
Object.hashCode()
,
Hashtable
int hashCode()
Object.hashCode()
.
Map.Entry.hashCode()
,
Object.equals(Object)
,
equals(Object)