org.datanucleus.util

Class ReferenceValueMap

java.lang.Object

org.datanucleus.util.ReferenceValueMap

All Implemented Interfaces:

Cloneable, Map

Direct Known Subclasses:

SoftValueMap, WeakValueMap

public abstract class ReferenceValueMap
extends Object
implements Map, Cloneable

A java.util.Map implementation using reference values.

The values are stored in the map as references. If the garbage collector clears the reference, the corresponding key is automatically removed from the map.

See Also:

Reference

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	ReferenceValueMap.ValueReference References returned by newValueReference must implement this interface to provide the corresponding map key for the value.

Nested classes/interfaces inherited from interface java.util.Map

Map.Entry<K,V>

Constructor Summary

Constructors

Constructor and Description
ReferenceValueMap() Default Constructor.
ReferenceValueMap(int initial_capacity) Constructor taking initial capacity.
ReferenceValueMap(int initial_capacity, float load_factor) Constructor taking initial capacity and load factor.
ReferenceValueMap(Map m) Constructor taking initial Map.

Method Summary

Modifier and Type	Method and Description
void	clear() Method to empty the HashMap.
Object	clone() Clone method.
boolean	containsKey(Object obj) Accessor for whether the Map contains the specified Key
boolean	containsValue(Object obj) Accessor for whether the Map contains the specified value.
Set	entrySet() Accessor for the entry set.
boolean	equals(Object o) Equality operator.
Object	get(Object key) Method to get a value for a key.
int	hashCode() Hashcode generator for this object.
boolean	isEmpty() Accessor for whether the Map is empty.
Set	keySet() Accessor for the Set of keys in the Map.
protected abstract ReferenceValueMap.ValueReference	newValueReference(Object key, Object value, ReferenceQueue queue) Returns a new Reference object to be inserted into the map.
Object	put(Object key, Object value) Method to add an object to the Map.
void	putAll(Map m) Method to add the contents of a Map.
void	reap() Utility method to reap objects.
Object	remove(Object key) Method to remove an object for the specified key.
int	size() Accessor for the size of the HashMap.
Collection	values() Accessor for the values from the Map.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Map

compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll

Constructor Detail

ReferenceValueMap

public ReferenceValueMap()

Default Constructor.

ReferenceValueMap

public ReferenceValueMap(int initial_capacity)

Constructor taking initial capacity.

Parameters:

initial_capacity - Initial Capacity of HashMap

ReferenceValueMap

public ReferenceValueMap(int initial_capacity,
                         float load_factor)

Constructor taking initial capacity and load factor.

Parameters:

initial_capacity - Initial Capacity of HashMap

load_factor - Load Factor of HashMap

ReferenceValueMap

public ReferenceValueMap(Map m)

Constructor taking initial Map.

Parameters:

m - Map to initial with.

Method Detail

clone

public Object clone()

Clone method.

Overrides:

clone in class Object

Returns:

Clone of this object.

newValueReference

protected abstract ReferenceValueMap.ValueReference newValueReference(Object key,
                                                                      Object value,
                                                                      ReferenceQueue queue)

Returns a new Reference object to be inserted into the map. Subclasses must implement this method to construct Reference objects of the desired type (e.g. SoftReference, etc.).

Parameters:

key - The key that will be inserted.

value - The associated value to be referenced.

queue - The ReferenceQueue with which to register the new Reference object.

Returns:

The new ValueReference

put

public Object put(Object key,
                  Object value)

Method to add an object to the Map.

Specified by:

put in interface Map

Parameters:

key - Key for object

value - Value of object

Returns:

The Object.

putAll

public void putAll(Map m)

Method to add the contents of a Map.

Specified by:

putAll in interface Map

Parameters:

m - Map

get

public Object get(Object key)

Method to get a value for a key.

Specified by:

get in interface Map

Parameters:

key - The Key

Returns:

The Value

clear

public void clear()

Method to empty the HashMap.

Specified by:

clear in interface Map

size

public int size()

Accessor for the size of the HashMap.

Specified by:

size in interface Map

Returns:

The size

containsKey

public boolean containsKey(Object obj)

Accessor for whether the Map contains the specified Key

Specified by:

containsKey in interface Map

Parameters:

obj - The key

Returns:

Whether the key exists

containsValue

public boolean containsValue(Object obj)

Accessor for whether the Map contains the specified value.

Specified by:

containsValue in interface Map

Parameters:

obj - The value

Returns:

Whether the Map contains the value.

isEmpty

public boolean isEmpty()

Accessor for whether the Map is empty.

Specified by:

isEmpty in interface Map

Returns:

Whether the Map is empty.

keySet

public Set keySet()

Accessor for the Set of keys in the Map.

Specified by:

keySet in interface Map

Returns:

The Set of keys

values

public Collection values()

Accessor for the values from the Map.

Specified by:

values in interface Map

Returns:

The Values.

entrySet

public Set entrySet()

Accessor for the entry set.

Specified by:

entrySet in interface Map

Returns:

The Set.

remove

public Object remove(Object key)

Method to remove an object for the specified key.

Specified by:

remove in interface Map

Parameters:

key - The Key

Returns:

The Object removed

hashCode

public int hashCode()

Hashcode generator for this object.

Specified by:

hashCode in interface Map

Overrides:

hashCode in class Object

Returns:

The Hashcode

equals

public boolean equals(Object o)

Equality operator.

Specified by:

equals in interface Map

Overrides:

equals in class Object

Parameters:

o - THe object to compare against.

Returns:

Whether it is equal.

reap

public void reap()

Utility method to reap objects.