Package com.sun.jdo.spi.persistence.utility

Class WeakValueHashMap

java.lang.Object

java.util.AbstractMap<K,V>

java.util.HashMap

com.sun.jdo.spi.persistence.utility.WeakValueHashMap

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

Nested Class Summary

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>

Constructor Summary

Constructors

Constructor	Description
WeakValueHashMap()

Method Summary

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 a Set 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 a Collection 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

Methods inherited from class java.util.AbstractMap

equals, hashCode, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

equals, hashCode

Constructor Details

WeakValueHashMap

public WeakValueHashMap()

Method Details

size

public int size()

Returns the number of key-value mappings in this map.

Specified by:

size in interface Map

Overrides:

size in class HashMap

Returns:

the number of key-value mappings in this map.

isEmpty

public boolean isEmpty()

Returns true if this map contains no key-value mappings.

Specified by:

isEmpty in interface Map

Overrides:

isEmpty in class HashMap

Returns:

true if this map contains no key-value mappings.

containsKey

public boolean containsKey(Object key)

Returns true if this map contains a mapping for the specified key.

Specified by:

containsKey in interface Map

Overrides:

containsKey in class HashMap

Parameters:

key - key whose presence in this map is to be tested

Returns:

true if this map contains a mapping for the specified key.

containsValue

public boolean containsValue(Object value)

Returns true if this map maps one or more keys to the specified value.

Specified by:

containsValue in interface Map

Overrides:

containsValue in class HashMap

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.

get

public Object get(Object key)

Gets the value for the given key.

Specified by:

get in interface Map

Overrides:

get in class HashMap

Parameters:

key - key whose associated value, if any, is to be returned

Returns:

the value to which this map maps the specified key.

put

public Object put(Object key,
 Object value)

Puts a new (key,value) into the map.

Specified by:

put in interface Map

Overrides:

put in class HashMap

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.

remove

public Object remove(Object key)

Removes key and value for the given key.

Specified by:

remove in interface Map

Overrides:

remove in class HashMap

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.

entrySet

public Set entrySet()

Returns a Set view of the mappings in this map.

Specified by:

entrySet in interface Map

Overrides:

entrySet in class HashMap

Returns:

a Set view of the mappings in this map.

values

public Collection values()

Returns a Collection view of the values contained in this map.

Specified by:

values in interface Map

Overrides:

values in class HashMap

Returns:

a Collection view of the values contained in this map.