Package org.apache.commons.collections4.list

Class CursorableLinkedList<E>

java.lang.Object
org.apache.commons.collections4.list.AbstractLinkedList<E>
org.apache.commons.collections4.list.CursorableLinkedList<E>
All Implemented Interfaces:
Serializable, Iterable<E>, Collection<E>, List<E>
public class CursorableLinkedList<E> extends AbstractLinkedList<E> 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 behavior.

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:
1.0
See Also:

  • Constructor Details

  • Method Details

    • addNode

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

    • broadcastNodeChanged

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

    • broadcastNodeInserted

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

    • broadcastNodeRemoved

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

    • createSubListListIterator

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

    • cursor

      public CursorableLinkedList.Cursor<E> 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<E> 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()).

    • init

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

    • iterator

      public Iterator<E> 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 behavior is available via listIterator().

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

    • listIterator

      public ListIterator<E> 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<E>
      Overrides:
      listIterator in class AbstractLinkedList<E>
      Returns:
      a new cursor iterator

    • listIterator

      public ListIterator<E> 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<E>
      Overrides:
      listIterator in class AbstractLinkedList<E>
      Parameters:
      fromIndex - the index to start from
      Returns:
      a new cursor iterator

    • registerCursor

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

    • removeAllNodes

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

    • removeNode

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

    • unregisterCursor

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

    • updateNode

      protected void updateNode(AbstractLinkedList.Node<E> node, E 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<E>
      Parameters:
      node - node to update
      value - new value of the node