org.apache.jdo.util

Class WeakValueHashMap

java.lang.Object

java.util.AbstractMap

java.util.HashMap

org.apache.jdo.util.WeakValueHashMap

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, java.util.Map

public class WeakValueHashMap
extends java.util.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

java.util.AbstractMap.SimpleEntry, java.util.AbstractMap.SimpleImmutableEntry

Constructor Summary

Constructors

Constructor and Description
WeakValueHashMap()

Method Summary

Methods

Modifier and Type	Method and Description
boolean	containsKey(java.lang.Object key) Returns true if this map contains a mapping for the specified key.
boolean	containsValue(java.lang.Object value) Returns true if this map maps one or more keys to the specified value.
java.util.Set	entrySet() Returns a Set view of the mappings in this map.
java.lang.Object	get(java.lang.Object key) Gets the value for the given key.
boolean	isEmpty() Returns true if this map contains no key-value mappings.
java.lang.Object	put(java.lang.Object key, java.lang.Object value) Puts a new (key,value) into the map.
java.lang.Object	remove(java.lang.Object key) Removes key and value for the given key.
int	size() Returns the number of key-value mappings in this map.
java.util.Collection	values() Returns a Collection view of the values contained in this map.

Methods inherited from class java.util.HashMap

clear, clone, keySet, putAll

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 Detail

WeakValueHashMap

public WeakValueHashMap()

Method Detail

size

public int size()

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

Specified by:

size in interface java.util.Map

Overrides:

size in class java.util.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 java.util.Map

Overrides:

isEmpty in class java.util.HashMap

Returns:

true if this map contains no key-value mappings.

containsKey

public boolean containsKey(java.lang.Object key)

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

Specified by:

containsKey in interface java.util.Map

Overrides:

containsKey in class java.util.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(java.lang.Object value)

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

Specified by:

containsValue in interface java.util.Map

Overrides:

containsValue in class java.util.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 java.lang.Object get(java.lang.Object key)

Gets the value for the given key.

Specified by:

get in interface java.util.Map

Overrides:

get in class java.util.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 java.lang.Object put(java.lang.Object key,
                   java.lang.Object value)

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

Specified by:

put in interface java.util.Map

Overrides:

put in class java.util.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 java.lang.Object remove(java.lang.Object key)

Removes key and value for the given key.

Specified by:

remove in interface java.util.Map

Overrides:

remove in class java.util.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 java.util.Set entrySet()

Returns a Set view of the mappings in this map.

Specified by:

entrySet in interface java.util.Map

Overrides:

entrySet in class java.util.HashMap

Returns:

a Set view of the mappings in this map.

values

public java.util.Collection values()

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

Specified by:

values in interface java.util.Map

Overrides:

values in class java.util.HashMap

Returns:

a Collection view of the values contained in this map.