Class WeakValueHashMap
- java.lang.Object
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- java.util.AbstractMap<K,V>
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- java.util.HashMap
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- com.sun.jdo.spi.persistence.utility.WeakValueHashMap
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- All Implemented Interfaces:
Serializable
,Cloneable
,Map
public class WeakValueHashMap extends HashMap
A WeakValueHashMap is implemented as a HashMap that maps keys to WeakValues. Because we don't have access to the innards of the HashMap, we have to wrap/unwrap value objects with WeakValues on every operation. Fortunately WeakValues are small, short-lived objects, so the added allocation overhead is tolerable. This implementaton directly extends java.util.HashMap.- Author:
- Markus Fuchs
- See Also:
HashMap
,WeakReference
, Serialized Form
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Nested Class Summary
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Nested classes/interfaces inherited from class java.util.AbstractMap
AbstractMap.SimpleEntry<K extends Object,V extends Object>, AbstractMap.SimpleImmutableEntry<K extends Object,V extends Object>
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Constructor Summary
Constructors Constructor Description WeakValueHashMap()
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description 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
entrySet()
Returns aSet
view of the mappings in this map.Object
get(Object key)
Gets the value for the given key.boolean
isEmpty()
Returns true if this map contains no key-value mappings.Object
put(Object key, Object value)
Puts a new (key,value) into the map.Object
remove(Object key)
Removes key and value for the given key.int
size()
Returns the number of key-value mappings in this map.Collection
values()
Returns aCollection
view of the values contained in this map.-
Methods inherited from class java.util.HashMap
clear, clone, compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, keySet, merge, putAll, putIfAbsent, remove, replace, replace, replaceAll
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Methods inherited from class java.util.AbstractMap
equals, hashCode, toString
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Method Detail
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size
public int size()
Returns the number of key-value mappings in this map.
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isEmpty
public boolean isEmpty()
Returns true if this map contains no key-value mappings.
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containsKey
public boolean containsKey(Object key)
Returns true if this map contains a mapping for the specified key.- Specified by:
containsKey
in interfaceMap
- Overrides:
containsKey
in classHashMap
- 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
public boolean containsValue(Object value)
Returns true if this map maps one or more keys to the specified value.- Specified by:
containsValue
in interfaceMap
- Overrides:
containsValue
in classHashMap
- Parameters:
value
- value whose presence in this map is to be tested- Returns:
- true if this map maps one or more keys to this value.
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put
public Object put(Object key, Object value)
Puts a new (key,value) into the map.- Specified by:
put
in interfaceMap
- Overrides:
put
in classHashMap
- Parameters:
key
- key with which the specified value is to be associated.value
- value to be associated with the specified key.- Returns:
- previous value associated with specified key, or null if there was no mapping for key or the value has been garbage collected by the garbage collector.
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remove
public Object remove(Object key)
Removes key and value for the given key.- Specified by:
remove
in interfaceMap
- Overrides:
remove
in classHashMap
- Parameters:
key
- key whose mapping is to be removed from the map.- Returns:
- previous value associated with specified key, or null if there was no mapping for key or the value has been garbage collected by the garbage collector.
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entrySet
public Set entrySet()
Returns aSet
view of the mappings in this map.
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values
public Collection values()
Returns aCollection
view of the values contained in this map.
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