Package org.datanucleus.store.types.wrappers.backed

Class LinkedHashSet<E>

  • All Implemented Interfaces:
    Serializable, Cloneable, Iterable<E>, Collection<E>, Set<E>, SCO<LinkedHashSet<E>>, SCOCollection<LinkedHashSet<E>,​E>, SCOContainer<LinkedHashSet<E>>, BackedSCO
    public class LinkedHashSet<E>
extends LinkedHashSet<E>
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 Detail

      • allowNulls

        protected transient boolean allowNulls

      • backingStore

        protected transient SetStore<E> backingStore

      • useCache

        protected transient boolean useCache

      • isCacheLoaded

        protected transient boolean isCacheLoaded

      • initialising

        protected transient boolean initialising

    • 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​(LinkedHashSet<E> newValue,
                       Object oldValue)
        Description copied from interface: SCO
        Method to initialise the SCO for use, where replacing an old value with a new value such as when calling a setter field passing in a new value. Note that oldValue is marked as Object since for cases where the member type is Collection the newValue could be, for example, ArrayList, and the oldValue of type Collection (representing null).
        Specified by:
        initialise in interface SCO<E>
        Overrides:
        initialise in class LinkedHashSet<E>
        Parameters:
        newValue - New value (to wrap)
        oldValue - Old value (to use in deciding what needs deleting etc)

      • 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<E>
        Overrides:
        load in class LinkedHashSet<E>

      • 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 BackedSCO
        Specified by:
        isLoaded in interface SCOContainer<E>
        Overrides:
        isLoaded in class LinkedHashSet<E>
        Returns:
        Whether it is loaded

      • loadFromStore

        protected void loadFromStore()
        Method to load all elements from the "backing store" where appropriate.

      • updateEmbeddedElement

        public void updateEmbeddedElement​(E element,
                                  int fieldNumber,
                                  Object value,
                                  boolean makeDirty)
        Method to update an embedded element in this collection.
        Specified by:
        updateEmbeddedElement in interface SCOCollection<LinkedHashSet<E>,​E>
        Overrides:
        updateEmbeddedElement in class LinkedHashSet<E>
        Parameters:
        element - The element
        fieldNumber - Number of field in the element
        value - New value for this field
        makeDirty - Whether to make the SCO field dirty.

      • unsetOwner

        public void unsetOwner()
        Method to unset the owner and backing store information.
        Specified by:
        unsetOwner in interface SCO<E>
        Overrides:
        unsetOwner in class LinkedHashSet<E>

      • clone

        public Object clone()
        Creates and returns a copy of this object.
        Specified by:
        clone in interface SCO<E>
        Overrides:
        clone in class LinkedHashSet<E>
        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<E>
        Specified by:
        contains in interface Set<E>
        Overrides:
        contains in class LinkedHashSet<E>
        Parameters:
        element - The element
        Returns:
        Whether it is contained.

      • isEmpty

        public boolean isEmpty()
        Accessor for whether the LinkedHashSet is empty.
        Specified by:
        isEmpty in interface Collection<E>
        Specified by:
        isEmpty in interface Set<E>
        Overrides:
        isEmpty in class LinkedHashSet<E>
        Returns:
        Whether it is empty.

      • size

        public int size()
        Accessor for the size of the LinkedHashSet.
        Specified by:
        size in interface Collection<E>
        Specified by:
        size in interface Set<E>
        Overrides:
        size in class LinkedHashSet<E>
        Returns:
        The size.

      • toArray

        public Object[] toArray​(Object[] a)
        Method to return the list as an array.
        Specified by:
        toArray in interface Collection<E>
        Specified by:
        toArray in interface Set<E>
        Overrides:
        toArray in class LinkedHashSet<E>
        Parameters:
        a - The runtime types of the array being defined by this param
        Returns:
        The array

      • add

        public boolean add​(E element)
        Method to add an element to the LinkedHashSet.
        Specified by:
        add in interface Collection<E>
        Specified by:
        add in interface Set<E>
        Overrides:
        add in class LinkedHashSet<E>
        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<E>
        Specified by:
        addAll in interface Set<E>
        Overrides:
        addAll in class LinkedHashSet<E>
        Parameters:
        elements - The collection
        Returns:
        Whether it was added ok.

      • remove

        public boolean remove​(Object element)
        Method to remove an element from the LinkedHashSet.
        Specified by:
        remove in interface Collection<E>
        Specified by:
        remove in interface Set<E>
        Overrides:
        remove in class LinkedHashSet<E>
        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<LinkedHashSet<E>,​E>
        Overrides:
        remove in class LinkedHashSet<E>
        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<E>
        Specified by:
        removeAll in interface Set<E>
        Overrides:
        removeAll in class LinkedHashSet<E>
        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<E>
        Specified by:
        retainAll in interface Set<E>
        Overrides:
        retainAll in class LinkedHashSet<E>
        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<E>
        Returns:
        the replaced object
        Throws:
        ObjectStreamException - if an error occurs