K
- the type of keys maintained by this mapV
- the type of mapped valuespublic class WeakValueHashMap<K,V> extends Object implements Map<K,V>
HashMap
,
WeakReference
Modifier and Type | Field and Description |
---|---|
static int |
INITIAL_CAPACITY
Default initial map capacity.
|
Constructor and Description |
---|
WeakValueHashMap()
Constructs an empty map with the default initial capacity (16) and the default load
factor (0.75).
|
WeakValueHashMap(int initialCapacity)
Constructs an empty map with the specified initial capacity and the default load factor (0.75).
|
Modifier and Type | Method and Description |
---|---|
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. |
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.
|
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. |
public static final int INITIAL_CAPACITY
public WeakValueHashMap()
public WeakValueHashMap(int initialCapacity)
initialCapacity
- the initial capacity.IllegalArgumentException
- if the initial capacity is negative.public void clear()
Map
public boolean containsKey(Object key)
Map
containsKey
in interface Map<K,V>
key
- key whose presence in this map is to be testedpublic boolean containsValue(Object value)
Map
containsValue
in interface Map<K,V>
value
- value whose presence in this map is to be testedpublic Set<Map.Entry<K,V>> entrySet()
Map
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.public V get(Object key)
Map
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.
public boolean isEmpty()
Map
public Set<K> keySet()
Map
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.public V put(K key, V value)
Map
m.containsKey(k)
would return true.)put
in interface Map<K,V>
key
- key with which the specified value is to be associatedvalue
- value to be associated with the specified keypublic void putAll(Map<? extends K,? extends V> m)
Map
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.public V remove(Object key)
Map
(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.
public int size()
Map
public Collection<V> values()
Map
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.