Package org.apache.commons.collections.list

Class CursorableLinkedList

java.lang.Object
org.apache.commons.collections.list.AbstractLinkedList
org.apache.commons.collections.list.CursorableLinkedList
All Implemented Interfaces:
Serializable, Iterable, Collection, List
public class CursorableLinkedList extends AbstractLinkedList implements Serializable
A List implementation with a ListIterator that allows concurrent modifications to the underlying list.

This implementation supports all of the optional List operations. It extends AbstractLinkedList and thus provides the stack/queue/dequeue operations available in LinkedList.

The main feature of this class is the ability to modify the list and the iterator at the same time. Both the listIterator() and cursor() methods provides access to a Cursor instance which extends ListIterator. The cursor allows changes to the list concurrent with changes to the iterator. Note that the iterator() method and sublists do not provide this cursor behaviour.

The Cursor class is provided partly for backwards compatibility and partly because it allows the cursor to be directly closed. Closing the cursor is optional because references are held via a WeakReference. For most purposes, simply modify the iterator and list at will, and then let the garbage collector to the rest.

Note that this implementation is not synchronized.

Since:
Commons Collections 1.0
Version:
$Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
Author:
Rodney Waldhoff, Janek Bogucki, Simon Kitching, Stephen Colebourne
See Also:

  • Field Details

    • cursors

      protected transient List cursors
      A list of the cursor currently open on this list

  • Constructor Details

    • CursorableLinkedList

      public CursorableLinkedList()
      Constructor that creates.

    • CursorableLinkedList

      public CursorableLinkedList(Collection coll)
      Constructor that copies the specified collection
      Parameters:
      coll - the collection to copy

  • Method Details

    • init

      protected void init()
      The equivalent of a default constructor called by any constructor and by readObject.
      Overrides:
      init in class AbstractLinkedList

    • iterator

      public Iterator iterator()
      Returns an iterator that does not support concurrent modification.

      If the underlying list is modified while iterating using this iterator a ConcurrentModificationException will occur. The cursor behaviour is available via listIterator().

      Specified by:
      iterator in interface Collection
      Specified by:
      iterator in interface Iterable
      Specified by:
      iterator in interface List
      Overrides:
      iterator in class AbstractLinkedList
      Returns:
      a new iterator that does not support concurrent modification

    • listIterator

      public ListIterator listIterator()
      Returns a cursor iterator that allows changes to the underlying list in parallel.

      The cursor enables iteration and list changes to occur in any order without invalidating the iterator (from one thread). When elements are added to the list, an event is fired to all active cursors enabling them to adjust to the change in the list.

      When the "current" (i.e., last returned by ListIterator.next() or ListIterator.previous()) element of the list is removed, the cursor automatically adjusts to the change (invalidating the last returned value such that it cannot be removed).

      Specified by:
      listIterator in interface List
      Overrides:
      listIterator in class AbstractLinkedList
      Returns:
      a new cursor iterator

    • listIterator

      public ListIterator listIterator(int fromIndex)
      Returns a cursor iterator that allows changes to the underlying list in parallel.

      The cursor enables iteration and list changes to occur in any order without invalidating the iterator (from one thread). When elements are added to the list, an event is fired to all active cursors enabling them to adjust to the change in the list.

      When the "current" (i.e., last returned by ListIterator.next() or ListIterator.previous()) element of the list is removed, the cursor automatically adjusts to the change (invalidating the last returned value such that it cannot be removed).

      Specified by:
      listIterator in interface List
      Overrides:
      listIterator in class AbstractLinkedList
      Parameters:
      fromIndex - the index to start from
      Returns:
      a new cursor iterator

    • cursor

      public CursorableLinkedList.Cursor cursor()
      Returns a CursorableLinkedList.Cursor for iterating through the elements of this list.

      A Cursor is a ListIterator with an additional close() method. Calling this method immediately discards the references to the cursor. If it is not called, then the garbage collector will still remove the reference as it is held via a WeakReference.

      The cursor enables iteration and list changes to occur in any order without invalidating the iterator (from one thread). When elements are added to the list, an event is fired to all active cursors enabling them to adjust to the change in the list.

      When the "current" (i.e., last returned by ListIterator.next() or ListIterator.previous()) element of the list is removed, the cursor automatically adjusts to the change (invalidating the last returned value such that it cannot be removed).

      The listIterator() method returns the same as this method, and can be cast to a Cursor if the close method is required.

      Returns:
      a new cursor iterator

    • cursor

      public CursorableLinkedList.Cursor cursor(int fromIndex)
      Returns a CursorableLinkedList.Cursor for iterating through the elements of this list starting from a specified index.

      A Cursor is a ListIterator with an additional close() method. Calling this method immediately discards the references to the cursor. If it is not called, then the garbage collector will still remove the reference as it is held via a WeakReference.

      The cursor enables iteration and list changes to occur in any order without invalidating the iterator (from one thread). When elements are added to the list, an event is fired to all active cursors enabling them to adjust to the change in the list.

      When the "current" (i.e., last returned by ListIterator.next() or ListIterator.previous()) element of the list is removed, the cursor automatically adjusts to the change (invalidating the last returned value such that it cannot be removed).

      The listIterator(int) method returns the same as this method, and can be cast to a Cursor if the close method is required.

      Parameters:
      fromIndex - the index to start from
      Returns:
      a new cursor iterator
      Throws:
      IndexOutOfBoundsException - if the index is out of range (index < 0 || index > size()).

    • updateNode

      protected void updateNode(AbstractLinkedList.Node node, Object value)
      Updates the node with a new value. This implementation sets the value on the node. Subclasses can override this to record the change.
      Overrides:
      updateNode in class AbstractLinkedList
      Parameters:
      node - node to update
      value - new value of the node

    • addNode

      protected void addNode(AbstractLinkedList.Node nodeToInsert, AbstractLinkedList.Node insertBeforeNode)
      Inserts a new node into the list.
      Overrides:
      addNode in class AbstractLinkedList
      Parameters:
      nodeToInsert - new node to insert
      insertBeforeNode - node to insert before
      Throws:
      NullPointerException - if either node is null

    • removeNode

      protected void removeNode(AbstractLinkedList.Node node)
      Removes the specified node from the list.
      Overrides:
      removeNode in class AbstractLinkedList
      Parameters:
      node - the node to remove
      Throws:
      NullPointerException - if node is null

    • removeAllNodes

      protected void removeAllNodes()
      Removes all nodes by iteration.
      Overrides:
      removeAllNodes in class AbstractLinkedList

    • registerCursor

      protected void registerCursor(CursorableLinkedList.Cursor cursor)
      Registers a cursor to be notified of changes to this list.
      Parameters:
      cursor - the cursor to register

    • unregisterCursor

      protected void unregisterCursor(CursorableLinkedList.Cursor cursor)
      Deregisters a cursor from the list to be notified of changes.
      Parameters:
      cursor - the cursor to deregister

    • broadcastNodeChanged

      protected void broadcastNodeChanged(AbstractLinkedList.Node node)
      Informs all of my registered cursors that the specified element was changed.
      Parameters:
      node - the node that was changed

    • broadcastNodeRemoved

      protected void broadcastNodeRemoved(AbstractLinkedList.Node node)
      Informs all of my registered cursors that the specified element was just removed from my list.
      Parameters:
      node - the node that was changed

    • broadcastNodeInserted

      protected void broadcastNodeInserted(AbstractLinkedList.Node node)
      Informs all of my registered cursors that the specified element was just added to my list.
      Parameters:
      node - the node that was changed

    • createSubListListIterator

      protected ListIterator createSubListListIterator(AbstractLinkedList.LinkedSubList subList, int fromIndex)
      Creates a list iterator for the sublist.
      Overrides:
      createSubListListIterator in class AbstractLinkedList
      Parameters:
      subList - the sublist to get an iterator for
      fromIndex - the index to start from, relative to the sublist