net.walend.collection
Class SoftHashMap

java.lang.Object
  |
  +--net.walend.collection.AbstractHashMap
        |
        +--net.walend.collection.SoftHashMap

All Implemented Interfaces:

java.lang.Cloneable, HasState, Map, MutableMap, java.io.Serializable

Direct Known Subclasses:

NullValueHashMap

public class SoftHashMap

extends AbstractHashMap

implements MutableMap

This MutableHashMap's values are held by soft references which may disapear if memory gets short. Be prepared for the occasional null value. This class is inherently multithreaded; get the guard from getGuard() if you need to keep other threads out of the map while you work.

Since:

20010827

Author:

David Walend

Nested Class Summary

private class

SoftHashMap.SoftEntry Entries for the hash map.

Nested classes inherited from class net.walend.collection.AbstractHashMap

Field Summary

private java.lang.Object

guard

Fields inherited from class net.walend.collection.AbstractHashMap

Fields inherited from interface net.walend.collection.Map

EMPTY

Constructor Summary

SoftHashMap()

SoftHashMap(Identitor identitor)

SoftHashMap(Identitor identitor, int capacity)

SoftHashMap(Identitor identitor, int capacity, float loadFactor)

SoftHashMap(int capacity)

SoftHashMap(int capacity, float loadFactor)

SoftHashMap(java.util.Map orig)

SoftHashMap(Map orig)

Method Summary

void	clear() Removes all key, value pairs from this Map.
boolean	containsAll(Map c) Returns true if this collection contains all of the Objects in the specified collection.
boolean	containsKey(java.lang.Object key) Returns true if this map contains an entry for key.
boolean	containsValue(java.lang.Object value) Returns true if this map contains value.
java.lang.Object	get(java.lang.Object key) Returns the value for the key.
java.lang.Object	getGuard() Return the synchronization guard for this SoftHashMap.
java.util.Map	getJavaMap() Return a java.util.Collection of these Objects.
Set	getKeys() Returns an immutable shallow copy of the Set of keys.
Collection	getValues() Returns an immutable shallow copy of the Collection of values.
boolean	isEmpty() Returns true if this Map has no entries.
java.util.Iterator	keyIterator() Returns an iterator over the keys.
protected AbstractHashMap.Entry	newEntry(int hash, java.lang.Object key, java.lang.Object value, AbstractHashMap.Entry next) Overridden to return entries with soft reference values.
java.lang.Object	put(java.lang.Object key, java.lang.Object value) Puts the key,value pair in the map.
void	putAll(Map map) Puts all of the key, value pairs in map into this Map.
java.lang.Object	remove(java.lang.Object key) Removes the key, value pair from this Map.
(package private) void	removeEntry(AbstractHashMap.Entry doomed) Removes the specified entry from this AbstractHashMap (and increments modCount).
boolean	sameContentsAs(Map c) Returns true if this Collection's contents are equal to c's.
boolean	sameStateAs(HasState victem) If two HasStates have the same internal state, return true.
int	size() Returns the number of key-value pairs in this map.
void	sweepNulls() Cleans out keys for null values.
java.util.Iterator	valueIterator() Returns an iterator over the values.

Methods inherited from class net.walend.collection.AbstractHashMap

capacity, clone, getIdentitor, getPrincipleInterface, loadFactor, toString

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface net.walend.collection.Map

getIdentitor

Methods inherited from interface net.walend.collection.HasState

getPrincipleInterface

Field Detail

guard

private final java.lang.Object guard

Constructor Detail

SoftHashMap

public SoftHashMap()

SoftHashMap

public SoftHashMap(int capacity)

SoftHashMap

public SoftHashMap(int capacity,
                   float loadFactor)

SoftHashMap

public SoftHashMap(Identitor identitor)

SoftHashMap

public SoftHashMap(Identitor identitor,
                   int capacity)

SoftHashMap

public SoftHashMap(Identitor identitor,
                   int capacity,
                   float loadFactor)

SoftHashMap

public SoftHashMap(java.util.Map orig)

SoftHashMap

public SoftHashMap(Map orig)

Method Detail

sameStateAs

public boolean sameStateAs(HasState victem)

If two HasStates have the same internal state, return true.

For objects with subobjects, Generally this method should only return true if the internal objects are equal. Implement a contentsHaveSameState() method to determine if the contents have the same state.

Specified by:

sameStateAs in interface HasState

Overrides:

sameStateAs in class AbstractHashMap

size

public int size()

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

This method calls sweepNulls(), and takes linear time.

Specified by:

size in interface Map

Overrides:

size in class AbstractHashMap

Following copied from class: net.walend.collection.AbstractHashMap

Returns:

the number of key-value mappings in this map.

isEmpty

public boolean isEmpty()

Returns true if this Map has no entries.

This method calls sweepNulls(), and takes linear time.

Specified by:

isEmpty in interface Map

Overrides:

isEmpty in class AbstractHashMap

Following copied from class: net.walend.collection.AbstractHashMap

Returns:

true if this map contains no key-value mappings.

containsKey

public boolean containsKey(java.lang.Object key)

Returns true if this map contains an entry for key.

Specified by:

containsKey in interface Map

Overrides:

containsKey in class AbstractHashMap

Throws:

java.lang.NullPointerException - if key is null.

containsValue

public boolean containsValue(java.lang.Object value)

Returns true if this map contains value.

Specified by:

containsValue in interface Map

Overrides:

containsValue in class AbstractHashMap

Throws:

java.lang.NullPointerException - if value is null.

get

public java.lang.Object get(java.lang.Object key)

Returns the value for the key. Returns null if the Map contains no value for key.

Specified by:

get in interface Map

Overrides:

get in class AbstractHashMap

Throws:

java.lang.NullPointerException - if the key is null.

getKeys

public Set getKeys()

Returns an immutable shallow copy of the Set of keys.

Specified by:

getKeys in interface Map

Overrides:

getKeys in class AbstractHashMap

Following copied from class: net.walend.collection.AbstractHashMap

Returns:

a set view of the keys contained in this map.

getValues

public Collection getValues()

Returns an immutable shallow copy of the Collection of values.

Specified by:

getValues in interface Map

Overrides:

getValues in class AbstractHashMap

Following copied from class: net.walend.collection.AbstractHashMap

Returns:

a collection view of the values contained in this map.

keyIterator

public java.util.Iterator keyIterator()

Returns an iterator over the keys.

This method calls sweepNulls(), and takes linear time.

Specified by:

keyIterator in interface Map

Overrides:

keyIterator in class AbstractHashMap

valueIterator

public java.util.Iterator valueIterator()

Returns an iterator over the values.

This method calls sweepNulls(), and takes linear time.

Specified by:

valueIterator in interface Map

Overrides:

valueIterator in class AbstractHashMap

containsAll

public boolean containsAll(Map c)

Returns true if this collection contains all of the Objects in the specified collection. This method uses the contains() method.

Specified by:

containsAll in interface Map

Overrides:

containsAll in class AbstractHashMap

sameContentsAs

public boolean sameContentsAs(Map c)

Returns true if this Collection's contents are equal to c's.

Specified by:

sameContentsAs in interface Map

Overrides:

sameContentsAs in class AbstractHashMap

getJavaMap

public java.util.Map getJavaMap()

Return a java.util.Collection of these Objects.

Specified by:

getJavaMap in interface Map

Overrides:

getJavaMap in class AbstractHashMap

removeEntry

void removeEntry(AbstractHashMap.Entry doomed)

Description copied from class: AbstractHashMap

Removes the specified entry from this AbstractHashMap (and increments modCount).

Overrides:

removeEntry in class AbstractHashMap

put

public java.lang.Object put(java.lang.Object key,
                            java.lang.Object value)

Puts the key,value pair in the map. Returns the previous value associated with key. If no value was associated, it returns null.

Specified by:

put in interface MutableMap

Overrides:

put in class AbstractHashMap

Throws:

java.lang.NullPointerException - if the key or value is null.

remove

public java.lang.Object remove(java.lang.Object key)

Removes the key, value pair from this Map. Returns the value associated with key, or null if no value was associated.

Specified by:

remove in interface MutableMap

Overrides:

remove in class AbstractHashMap

Throws:

java.lang.NullPointerException - if the key is null.

putAll

public void putAll(Map map)

Puts all of the key, value pairs in map into this Map. map's pairs replace any conflicting pairs in this Map.

Specified by:

putAll in interface MutableMap

Overrides:

putAll in class AbstractHashMap

Throws:

java.lang.NullPointerException - if map is null.

clear

public void clear()

Removes all key, value pairs from this Map.

Specified by:

clear in interface MutableMap

Overrides:

clear in class AbstractHashMap

newEntry

protected AbstractHashMap.Entry newEntry(int hash,
                                         java.lang.Object key,
                                         java.lang.Object value,
                                         AbstractHashMap.Entry next)

Overridden to return entries with soft reference values.

Overrides:

newEntry in class AbstractHashMap

sweepNulls

public void sweepNulls()

Cleans out keys for null values. It scans the table, so don't call it without a good reason.

getGuard

public final java.lang.Object getGuard()

Return the synchronization guard for this SoftHashMap. Don't stand on this guard for too long; the garbage collection thread uses it to clear out SoftReferences.