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

Class Queue<E>

  • All Implemented Interfaces:
    Serializable, Cloneable, Iterable<E>, Collection<E>, Queue<E>, SCO<Queue<E>>, SCOCollection<Queue<E>,​E>, SCOContainer<Queue<E>>, BackedSCO
    public class Queue<E>
extends Queue<E>
implements BackedSCO
    A mutable second-class Queue object. This class extends AbstractQueue, using that class to contain the current objects, and the backing CollectionStore 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

      • backingStore

        protected transient ListStore<E> backingStore

      • allowNulls

        protected transient boolean allowNulls

      • useCache

        protected transient boolean useCache

      • isCacheLoaded

        protected transient boolean isCacheLoaded

    • Method Detail

      • initialise

        public void initialise​(Queue 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 Queue<E>
        Parameters:
        newValue - New value (to wrap)
        oldValue - Old value (to use in deciding what needs deleting etc)

      • initialise

        public void initialise​(Queue c)
        Method to initialise the SCO from an existing value.
        Specified by:
        initialise in interface SCO<E>
        Overrides:
        initialise in class Queue<E>
        Parameters:
        c - The object to set from

      • initialise

        public void initialise()
        Method to initialise the SCO for use.
        Specified by:
        initialise in interface SCO<E>
        Overrides:
        initialise in class Queue<E>

      • getValue

        public Queue getValue()
        Accessor for the unwrapped value that we are wrapping.
        Specified by:
        getValue in interface SCO<E>
        Overrides:
        getValue in class Queue<E>
        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<E>
        Overrides:
        load in class Queue<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 Queue<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<Queue<E>,​E>
        Overrides:
        updateEmbeddedElement in class Queue<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 field information.
        Specified by:
        unsetOwner in interface SCO<E>
        Overrides:
        unsetOwner in class Queue<E>

      • clone

        public Object clone()
        Creates and returns a copy of this object.

        Mutable second-class Objects are required to provide a public clone method in order to allow for copying persistable objects. In contrast to Object.clone(), this method must not throw a CloneNotSupportedException.

        Specified by:
        clone in interface SCO<E>
        Overrides:
        clone in class Queue<E>
        Returns:
        A clone of the object

      • contains

        public boolean contains​(Object element)
        Accessor for whether an element is contained in the Collection.
        Specified by:
        contains in interface Collection<E>
        Overrides:
        contains in class Queue<E>
        Parameters:
        element - The element
        Returns:
        Whether the element is contained here

      • containsAll

        public boolean containsAll​(Collection c)
        Accessor for whether a collection of elements are contained here.
        Specified by:
        containsAll in interface Collection<E>
        Overrides:
        containsAll in class Queue<E>
        Parameters:
        c - The collection of elements.
        Returns:
        Whether they are contained.

      • equals

        public boolean equals​(Object o)
        Equality operator.
        Specified by:
        equals in interface Collection<E>
        Overrides:
        equals in class Queue<E>
        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<E>
        Overrides:
        hashCode in class Queue<E>
        Returns:
        The Hash code.

      • isEmpty

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

      • peek

        public E peek()
        Method to peek at the next element in the Queue.
        Specified by:
        peek in interface Queue<E>
        Overrides:
        peek in class Queue<E>
        Returns:
        The element

      • size

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

      • toArray

        public Object[] toArray()
        Method to return the Collection as an array.
        Specified by:
        toArray in interface Collection<E>
        Overrides:
        toArray in class Queue<E>
        Returns:
        The array

      • toArray

        public Object[] toArray​(Object[] a)
        Method to return the Collection as an array.
        Specified by:
        toArray in interface Collection<E>
        Overrides:
        toArray in class Queue<E>
        Parameters:
        a - The array to write the results to
        Returns:
        The array

      • add

        public boolean add​(E element)
        Method to add an element to the Collection.
        Specified by:
        add in interface Collection<E>
        Specified by:
        add in interface Queue<E>
        Overrides:
        add in class Queue<E>
        Parameters:
        element - The element to add
        Returns:
        Whether it was added successfully.

      • addAll

        public boolean addAll​(Collection elements)
        Method to add a collection of elements.
        Specified by:
        addAll in interface Collection<E>
        Overrides:
        addAll in class Queue<E>
        Parameters:
        elements - The collection of elements to add.
        Returns:
        Whether they were added successfully.

      • clear

        public void clear()
        Method to clear the Collection.
        Specified by:
        clear in interface Collection<E>
        Overrides:
        clear in class Queue<E>

      • offer

        public boolean offer​(E element)
        Method to offer an element to the Queue.
        Specified by:
        offer in interface Queue<E>
        Overrides:
        offer in class Queue<E>
        Parameters:
        element - The element to offer
        Returns:
        Whether it was added successfully.

      • poll

        public E poll()
        Method to poll the next element in the Queue.
        Specified by:
        poll in interface Queue<E>
        Overrides:
        poll in class Queue<E>
        Returns:
        The element (now removed)

      • remove

        public boolean remove​(Object element)
        Method to remove an element from the Collection.
        Specified by:
        remove in interface Collection<E>
        Overrides:
        remove in class Queue<E>
        Parameters:
        element - The Element to remove
        Returns:
        Whether it was removed successfully.

      • 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<Queue<E>,​E>
        Overrides:
        remove in class Queue<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 a Collection of elements.
        Specified by:
        removeAll in interface Collection<E>
        Overrides:
        removeAll in class Queue<E>
        Parameters:
        elements - The collection to remove
        Returns:
        Whether they were removed successfully.

      • retainAll

        public boolean retainAll​(Collection c)
        Method to retain a Collection of elements (and remove all others).
        Specified by:
        retainAll in interface Collection<E>
        Overrides:
        retainAll in class Queue<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 Queue<E>
        Returns:
        the replaced object
        Throws:
        ObjectStreamException - if an error occurs