org.datanucleus.store.types.backed

Class LinkedHashSet

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractSet<E>

java.util.HashSet<E>

java.util.LinkedHashSet

org.datanucleus.store.types.simple.LinkedHashSet

org.datanucleus.store.types.backed.LinkedHashSet

All Implemented Interfaces:

Serializable, Cloneable, Iterable, Collection, Set, BackedSCO, SCO, SCOCollection, SCOContainer, SCOMtoN

public class LinkedHashSet
extends LinkedHashSet
implements BackedSCO

A mutable second-class LinkedHashSet object. This class extends LinkedHashSet, using that class to contain the current objects, and the backing SetStore to be the interface to the datastore. A "backing store" is not present for datastores that dont use DatastoreClass, or if the container is serialised or non-persistent.

Modes of Operation

The user can operate the list in 2 modes. The cached mode will use an internal cache of the elements (in the "delegate") reading them at the first opportunity and then using the cache thereafter. The non-cached mode will just go direct to the "backing store" each call.

Mutators

When the "backing store" is present any updates are passed direct to the datastore as well as to the "delegate". If the "backing store" isn't present the changes are made to the "delegate" only.

Accessors

When any accessor method is invoked, it typically checks whether the container has been loaded from its "backing store" (where present) and does this as necessary. Some methods (size()) just check if everything is loaded and use the delegate if possible, otherwise going direct to the datastore.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	allowNulls
protected SetStore	backingStore
protected boolean	isCacheLoaded
protected boolean	queued
protected boolean	useCache

Fields inherited from class org.datanucleus.store.types.simple.LinkedHashSet

delegate, LOCALISER, ownerMmd, ownerOP

Constructor Summary

Constructors

Constructor and Description
LinkedHashSet(ObjectProvider op, AbstractMemberMetaData mmd) Constructor, using the ObjectProvider of the "owner" and the field name.

Method Summary

Methods

Modifier and Type	Method and Description
boolean	add(Object element) Method to add an element to the LinkedHashSet.
boolean	addAll(Collection elements) Method to add a collection to the LinkedHashSet.
void	clear() Method to clear the LinkedHashSet
Object	clone() Creates and returns a copy of this object.
boolean	contains(Object element) Accessor for whether an element is contained in this Set.
boolean	containsAll(Collection c) Accessor for whether a collection is contained in this Set.
boolean	equals(Object o) Equality operator.
Store	getBackingStore()
Object	getValue() Accessor for the unwrapped value that we are wrapping.
int	hashCode() Hashcode operator.
void	initialise() Method to initialise the SCO for use.
void	initialise(Object o, boolean forInsert, boolean forUpdate) Method to initialise the SCO from an existing value.
boolean	isEmpty() Accessor for whether the LinkedHashSet is empty.
boolean	isLoaded() Method to return if the SCO has its contents loaded.
Iterator	iterator() Accessor for an iterator for the Set.
void	load() Method to effect the load of the data in the SCO.
protected void	loadFromStore() Method to load all elements from the "backing store" where appropriate.
boolean	remove(Object element) Method to remove an element from the LinkedHashSet.
boolean	remove(Object element, boolean allowCascadeDelete) Method to remove an element from the collection, and observe the flag for whether to allow cascade delete.
boolean	removeAll(Collection elements) Method to remove all elements from the collection from the LinkedHashSet.
boolean	retainAll(Collection c) Method to retain a Collection of elements (and remove all others).
int	size() Accessor for the size of the LinkedHashSet.
Object[]	toArray() Method to return the list as an array.
Object[]	toArray(Object[] a) Method to return the list as an array.
void	unsetOwner() Method to unset the owner and backing store information.
void	updateEmbeddedElement(Object element, int fieldNumber, Object value) Method to update an embedded element in this collection.
protected Object	writeReplace() The writeReplace method is called when ObjectOutputStream is preparing to write the object to the stream.

Methods inherited from class org.datanucleus.store.types.simple.LinkedHashSet

attachCopy, detachCopy, getFieldName, getOwner, makeDirty

Methods inherited from class java.util.AbstractCollection

toString

Methods inherited from class java.lang.Object

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

Field Detail

allowNulls

protected transient boolean allowNulls

backingStore

protected transient SetStore backingStore

useCache

protected transient boolean useCache

isCacheLoaded

protected transient boolean isCacheLoaded

queued

protected transient boolean queued

Constructor Detail

LinkedHashSet

public LinkedHashSet(ObjectProvider op,
             AbstractMemberMetaData mmd)

Constructor, using the ObjectProvider of the "owner" and the field name.

Parameters:

op - The owner ObjectProvider

mmd - Metadata for the member

Method Detail

initialise

public void initialise(Object o,
              boolean forInsert,
              boolean forUpdate)

Method to initialise the SCO from an existing value.

Specified by:

initialise in interface SCO

Overrides:

initialise in class LinkedHashSet

Parameters:

o - The object to set from

forInsert - Whether the object needs inserting in the datastore with this value

forUpdate - Whether to update the datastore with this value

initialise

public void initialise()

Method to initialise the SCO for use.

Specified by:

initialise in interface SCO

Overrides:

initialise in class LinkedHashSet

getValue

public Object getValue()

Accessor for the unwrapped value that we are wrapping.

Specified by:

getValue in interface SCO

Overrides:

getValue in class LinkedHashSet

Returns:

The unwrapped value

load

public void load()

Method to effect the load of the data in the SCO. Used when the SCO supports lazy-loading to tell it to load all now.

Specified by:

load in interface SCOContainer

Overrides:

load in class LinkedHashSet

isLoaded

public boolean isLoaded()

Method to return if the SCO has its contents loaded. If the SCO doesn't support lazy loading will just return true.

Specified by:

isLoaded in interface SCOContainer

Overrides:

isLoaded in class LinkedHashSet

Returns:

Whether it is loaded

loadFromStore

protected void loadFromStore()

Method to load all elements from the "backing store" where appropriate.

getBackingStore

public Store getBackingStore()

Specified by:

getBackingStore in interface BackedSCO

updateEmbeddedElement

public void updateEmbeddedElement(Object element,
                         int fieldNumber,
                         Object value)

Method to update an embedded element in this collection.

Specified by:

updateEmbeddedElement in interface SCOCollection

Overrides:

updateEmbeddedElement in class LinkedHashSet

Parameters:

element - The element

fieldNumber - Number of field in the element

value - New value for this field

unsetOwner

public void unsetOwner()

Method to unset the owner and backing store information.

Specified by:

unsetOwner in interface SCO

Overrides:

unsetOwner in class LinkedHashSet

clone

public Object clone()

Creates and returns a copy of this object.

Specified by:

clone in interface SCO

Overrides:

clone in class LinkedHashSet

Returns:

The cloned object

contains

public boolean contains(Object element)

Accessor for whether an element is contained in this Set.

Specified by:

contains in interface Collection

Specified by:

contains in interface Set

Specified by:

contains in interface SCOMtoN

Overrides:

contains in class LinkedHashSet

Parameters:

element - The element

Returns:

Whether it is contained.

containsAll

public boolean containsAll(Collection c)

Accessor for whether a collection is contained in this Set.

Specified by:

containsAll in interface Collection

Specified by:

containsAll in interface Set

Overrides:

containsAll in class LinkedHashSet

Parameters:

c - The collection

Returns:

Whether it is contained.

equals

public boolean equals(Object o)

Equality operator.

Specified by:

equals in interface Collection

Specified by:

equals in interface Set

Overrides:

equals in class LinkedHashSet

Parameters:

o - The object to compare against.

Returns:

Whether this object is the same.

hashCode

public int hashCode()

Hashcode operator.

Specified by:

hashCode in interface Collection

Specified by:

hashCode in interface Set

Overrides:

hashCode in class LinkedHashSet

Returns:

The Hash code.

isEmpty

public boolean isEmpty()

Accessor for whether the LinkedHashSet is empty.

Specified by:

isEmpty in interface Collection

Specified by:

isEmpty in interface Set

Overrides:

isEmpty in class LinkedHashSet

Returns:

Whether it is empty.

iterator

public Iterator iterator()

Accessor for an iterator for the Set.

Specified by:

iterator in interface Iterable

Specified by:

iterator in interface Collection

Specified by:

iterator in interface Set

Overrides:

iterator in class LinkedHashSet

Returns:

The iterator

size

public int size()

Accessor for the size of the LinkedHashSet.

Specified by:

size in interface Collection

Specified by:

size in interface Set

Overrides:

size in class LinkedHashSet

Returns:

The size.

toArray

public Object[] toArray()

Method to return the list as an array.

Specified by:

toArray in interface Collection

Specified by:

toArray in interface Set

Overrides:

toArray in class LinkedHashSet

Returns:

The array

toArray

public Object[] toArray(Object[] a)

Method to return the list as an array.

Specified by:

toArray in interface Collection

Specified by:

toArray in interface Set

Overrides:

toArray in class LinkedHashSet

Parameters:

a - The runtime types of the array being defined by this param

Returns:

The array

add

public boolean add(Object element)

Method to add an element to the LinkedHashSet.

Specified by:

add in interface Collection

Specified by:

add in interface Set

Overrides:

add in class LinkedHashSet

Parameters:

element - The new element

Returns:

Whether it was added ok.

addAll

public boolean addAll(Collection elements)

Method to add a collection to the LinkedHashSet.

Specified by:

addAll in interface Collection

Specified by:

addAll in interface Set

Overrides:

addAll in class LinkedHashSet

Parameters:

elements - The collection

Returns:

Whether it was added ok.

clear

public void clear()

Method to clear the LinkedHashSet

Specified by:

clear in interface Collection

Specified by:

clear in interface Set

Overrides:

clear in class LinkedHashSet

remove

public boolean remove(Object element)

Method to remove an element from the LinkedHashSet.

Specified by:

remove in interface Collection

Specified by:

remove in interface Set

Overrides:

remove in class LinkedHashSet

Parameters:

element - The element

Returns:

Whether it was removed ok.

remove

public boolean remove(Object element,
             boolean allowCascadeDelete)

Method to remove an element from the collection, and observe the flag for whether to allow cascade delete.

Specified by:

remove in interface SCOCollection

Overrides:

remove in class LinkedHashSet

Parameters:

element - The element

allowCascadeDelete - Whether to allow cascade delete

Returns:

Whether it was removed successfully.

removeAll

public boolean removeAll(Collection elements)

Method to remove all elements from the collection from the LinkedHashSet.

Specified by:

removeAll in interface Collection

Specified by:

removeAll in interface Set

Overrides:

removeAll in class LinkedHashSet

Parameters:

elements - The collection of elements to remove

Returns:

Whether it was removed ok.

retainAll

public boolean retainAll(Collection c)

Method to retain a Collection of elements (and remove all others).

Specified by:

retainAll in interface Collection

Specified by:

retainAll in interface Set

Overrides:

retainAll in class LinkedHashSet

Parameters:

c - The collection to retain

Returns:

Whether they were retained successfully.

writeReplace

protected Object writeReplace()
                       throws ObjectStreamException

The writeReplace method is called when ObjectOutputStream is preparing to write the object to the stream. The ObjectOutputStream checks whether the class defines the writeReplace method. If the method is defined, the writeReplace method is called to allow the object to designate its replacement in the stream. The object returned should be either of the same type as the object passed in or an object that when read and resolved will result in an object of a type that is compatible with all references to the object.

Overrides:

writeReplace in class LinkedHashSet

Returns:

the replaced object

Throws:

ObjectStreamException