org.apache.commons.collections
Class SoftRefHashMap

java.lang.Object
  |
  +--org.apache.commons.collections.SoftRefHashMap

All Implemented Interfaces:

Map

public class SoftRefHashMap

extends Object

implements Map

HashMap with SoftReference links to values which allows the values of the Map to be garbage collected by the JVM if it becomes low on memory. Derive from this class and override the factory method createReference() method to make a Map wrapped in other types of Reference.

A synchronized version can be obtained with: Collections.synchronizedMap( theMapToSynchronize )

WARNING the values() and entrySet() methods require optimisation like the standard HashMap implementations so that iteration over this Map is efficient.

Author:

James.Dodd, James Strachan

Inner classes inherited from class java.util.Map

Map.Entry

Constructor Summary

SoftRefHashMap()

Method Summary

void	clear() Clears all mappings
boolean	containsKey(Object key) Answers whether the argument is in the domain of the mappings
boolean	containsValue(Object value) Answers whether the argument is a Referenced value
protected Reference	createReference(Object referent) Returns a reference to the argument.
Set	entrySet() Returns a set view of the mappings in the wrapped map
boolean	equals(Object object) Answers whether this map and the argument are 'the same'
Object	get(Object key) Retrieves the referent of the Referenced value
protected Map	getMap() Retrieves the wrapped HashMap
int	hashCode() Calculates the hash code for this map
boolean	isEmpty() Answers whether there are any mappings
Set	keySet() Returns the domain of the mappings
void	purge() Removes References that have had their referents garbage collected
Object	put(Object key, Object value) Adds a key-value mapping, wrapping the value in a Reference
void	putAll(Map map) Put all of the mappings in the argument into this wrapped map
Object	remove(Object key) Removes a mapping from this map
int	size() Returns the number of mappings in this map
Collection	values() Returns a collection of the Referenced values

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SoftRefHashMap

public SoftRefHashMap()

Method Detail

clear

public void clear()

Clears all mappings

Specified by:

clear in interface Map

containsKey

public boolean containsKey(Object key)

Answers whether the argument is in the domain of the mappings

Specified by:

containsKey in interface Map

containsValue

public boolean containsValue(Object value)

Answers whether the argument is a Referenced value

Specified by:

containsValue in interface Map

createReference

protected Reference createReference(Object referent)

Returns a reference to the argument. Override this method to make wrapped maps for other Reference types

entrySet

public Set entrySet()

Returns a set view of the mappings in the wrapped map

Specified by:

entrySet in interface Map

equals

public boolean equals(Object object)

Answers whether this map and the argument are 'the same'

Specified by:

equals in interface Map

Overrides:

equals in class Object

get

public Object get(Object key)

Retrieves the referent of the Referenced value

Specified by:

get in interface Map

Parameters:

key - The key with which to retrieve the value

getMap

protected Map getMap()

Retrieves the wrapped HashMap

Returns:

The wrapped HashMap

hashCode

public int hashCode()

Calculates the hash code for this map

Specified by:

hashCode in interface Map

Overrides:

hashCode in class Object

isEmpty

public boolean isEmpty()

Answers whether there are any mappings

Specified by:

isEmpty in interface Map

keySet

public Set keySet()

Returns the domain of the mappings

Specified by:

keySet in interface Map

purge

public void purge()

Removes References that have had their referents garbage collected

put

public Object put(Object key,
                  Object value)

Adds a key-value mapping, wrapping the value in a Reference

Specified by:

put in interface Map

putAll

public void putAll(Map map)

Put all of the mappings in the argument into this wrapped map

Specified by:

putAll in interface Map

remove

public Object remove(Object key)

Removes a mapping from this map

Specified by:

remove in interface Map

size

public int size()

Returns the number of mappings in this map

Specified by:

size in interface Map

values

public Collection values()

Returns a collection of the Referenced values

Specified by:

values in interface Map