java.lang.Object | ||
↳ | java.util.AbstractMap<K, V> | |
↳ | java.util.WeakHashMap<K, V> |
WeakHashMap is an implementation of Map with keys which are WeakReferences. A key/value mapping is removed when the key is no longer referenced. All optional operations (adding and removing) are supported. Keys and values can be any objects. Note that the garbage collector acts similar to a second thread on this collection, possibly removing keys.
Public Constructors | |||||||||||
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Constructs a new empty
WeakHashMap instance. | |||||||||||
Constructs a new
WeakHashMap instance with the specified
capacity. | |||||||||||
Constructs a new
WeakHashMap instance with the specified capacity
and load factor. | |||||||||||
Constructs a new
WeakHashMap instance containing the mappings
from the specified map. |
Public Methods | |||||||||||
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Removes all mappings from this map, leaving it empty.
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Returns whether this map contains the specified key.
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Returns whether this map contains the specified value.
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Returns a set containing all of the mappings in this map.
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Returns the value of the mapping with the specified key.
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Returns the number of elements in this map.
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Returns a set of the keys contained in this map.
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Maps the specified key to the specified value.
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Copies all the mappings in the given map to this map.
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Removes the mapping with the specified key from this map.
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Returns the number of elements in this map.
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Returns a collection of the values contained in this map.
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Inherited Methods | |||||||||||
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From class java.util.AbstractMap
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From class java.lang.Object
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From interface java.util.Map
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Constructs a new WeakHashMap
instance with the specified
capacity.
capacity | the initial capacity of this map. |
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IllegalArgumentException | if the capacity is less than zero. |
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Constructs a new WeakHashMap
instance with the specified capacity
and load factor.
capacity | the initial capacity of this map. |
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loadFactor | the initial load factor. |
IllegalArgumentException | if the capacity is less than zero or the load factor is less or equal to zero. |
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Constructs a new WeakHashMap
instance containing the mappings
from the specified map.
map | the mappings to add. |
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Returns whether this map contains the specified key.
key | the key to search for. |
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true
if this map contains the specified key,
false
otherwise.
Returns whether this map contains the specified value.
value | the value to search for. |
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true
if this map contains the specified value,
false
otherwise.
Returns a set containing all of the mappings in this map. Each mapping is
an instance of Map.Entry
. As the set is backed by this map,
changes in one will be reflected in the other. It does not support adding
operations.
Returns the value of the mapping with the specified key.
key | the key. |
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null
if no mapping for the specified key is found.
Returns the number of elements in this map.
Returns a set of the keys contained in this map. The set is backed by this map so changes to one are reflected by the other. The set does not support adding.
Maps the specified key to the specified value.
key | the key. |
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value | the value. |
null
if there was no mapping.
Copies all the mappings in the given map to this map. These mappings will replace all mappings that this map had for any of the keys currently in the given map.
map | the map to copy mappings from. |
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NullPointerException | if map is null .
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Removes the mapping with the specified key from this map.
key | the key of the mapping to remove. |
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null
if no mapping
for the specified key was found.
Returns the number of elements in this map.
Returns a collection of the values contained in this map. The collection is backed by this map so changes to one are reflected by the other. The collection supports remove, removeAll, retainAll and clear operations, and it does not support add or addAll operations.
This method returns a collection which is the subclass of AbstractCollection. The iterator method of this subclass returns a "wrapper object" over the iterator of map's entrySet(). The size method wraps the map's size method and the contains method wraps the map's containsValue method.
The collection is created when this method is called at first time and returned in response to all subsequent calls. This method may return different Collection when multiple calls to this method, since it has no synchronization performed.