Class WeakMapCache<K,V>
- All Implemented Interfaces:
ICache<K,
V>
HashMap
with WeakReference
s.- Author:
- ralph
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Constructor Summary
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Method Summary
Modifier and TypeMethodDescriptionvoid
clear()
Removes all of the mappings from this map (optional operation).protected void
clearMap()
Clears the map by working on the reference queue.boolean
containsKey
(Object key) Returnstrue
if this map contains a mapping for the specified key.boolean
containsValue
(Object value) Returnstrue
if this map maps one or more keys to the specified value.Returns the value to which the specified key is mapped, ornull
if this map contains no mapping for the key.boolean
isEmpty()
Returnstrue
if this map contains no key-value mappings.keySet()
Returns aSet
view of the keys contained in this map.Associates the specified value with the specified key in this map (optional operation).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.values()
Returns aCollection
view of the values contained in this map.
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Constructor Details
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WeakMapCache
public WeakMapCache()Constructor.
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Method Details
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size
public int size()Returns the number of key-value mappings in this map. If the map contains more thanInteger.MAX_VALUE
elements, returnsInteger.MAX_VALUE
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isEmpty
public boolean isEmpty()Returnstrue
if this map contains no key-value mappings. -
containsKey
Returnstrue
if this map contains a mapping for the specified key. More formally, returnstrue
if and only if this map contains a mapping for a keyk
such that(key==null ? k==null : key.equals(k))
. (There can be at most one such mapping.)- Specified by:
containsKey
in interfaceICache<K,
V> - Parameters:
key
- key whose presence in this map is to be tested- Returns:
true
if this map contains a mapping for the specified key
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containsValue
Returnstrue
if this map maps one or more keys to the specified value. More formally, returnstrue
if and only if this map contains at least one mapping to a valuev
such that(value==null ? v==null : value.equals(v))
. This operation will probably require time linear in the map size for most implementations of theMap
interface.- Specified by:
containsValue
in interfaceICache<K,
V> - Parameters:
value
- value whose presence in this map is to be tested- Returns:
true
if this map maps one or more keys to the specified value
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get
Returns the value to which the specified key is mapped, ornull
if this map contains no mapping for the key.More formally, if this map contains a mapping from a key
k
to a valuev
such that(key==null ? k==null : key.equals(k))
, then this method returnsv
; otherwise it returnsnull
. (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 tonull
. ThecontainsKey
operation may be used to distinguish these two cases. -
clearMap
protected void clearMap()Clears the map by working on the reference queue. -
put
Associates the specified value with the specified key in this map (optional operation). If the map previously contained a mapping for the key, the old value is replaced by the specified value. (A mapm
is said to contain a mapping for a keyk
if and only ifm.containsKey(k)
would returntrue
.)- Specified by:
put
in interfaceICache<K,
V> - Parameters:
key
- key with which the specified value is to be associatedvalue
- value to be associated with the specified key- Returns:
- the previous value associated with
key
, ornull
if there was no mapping forkey
. (Anull
return can also indicate that the map previously associatednull
withkey
, if the implementation supportsnull
values.)
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remove
Removes the mapping for a key from this map if it is present (optional operation). More formally, if this map contains a mapping from keyk
to valuev
such that(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 tonull
.The map will not contain a mapping for the specified key once the call returns.
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clear
public void clear()Removes all of the mappings from this map (optional operation). The map will be empty after this call returns. -
keySet
Returns aSet
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 ownremove
operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via theIterator.remove
,Set.remove
,removeAll
,retainAll
, andclear
operations. It does not support theadd
oraddAll
operations. -
values
Returns aCollection
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 ownremove
operation), the results of the iteration are undefined. The collection supports element removal, which removes the corresponding mapping from the map, via theIterator.remove
,Collection.remove
,removeAll
,retainAll
andclear
operations. It does not support theadd
oraddAll
operations.
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