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## 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:
  Collection, List, Serializable

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: 1.5 $ $Date: 2004/02/18 01:12:26 $
Author:
  Rodney Waldhoff, Janek Bogucki, Simon Kitching, Stephen Colebourne
See Also:
  `LinkedList`, Serialized Form

Nested Class Summary
`static class` | `CursorableLinkedList.Cursor` An extended `ListIterator` that allows concurrent changes to the underlying list.

Nested classes inherited from class org.apache.commons.collections.list.AbstractLinkedList
`AbstractLinkedList.LinkedSubList, AbstractLinkedList.LinkedSubListIterator, AbstractLinkedList.Node`

Field Summary
`protected List` | `cursors` A list of the cursor currently open on this list

Fields inherited from class org.apache.commons.collections.list.AbstractLinkedList
`header, modCount, size`

Constructor Summary
`CursorableLinkedList()` Constructor that creates.
`CursorableLinkedList(Collection coll)` Constructor that copies the specified collection

Method Summary
`protected void` | `addNode(AbstractLinkedList.Node nodeToInsert, AbstractLinkedList.Node insertBeforeNode)` Inserts a new node into the list.
`protected void` | `broadcastNodeChanged(AbstractLinkedList.Node node)` Informs all of my registered cursors that the specified element was changed.
`protected void` | `broadcastNodeInserted(AbstractLinkedList.Node node)` Informs all of my registered cursors that the specified element was just added to my list.
`protected void` | `broadcastNodeRemoved(AbstractLinkedList.Node node)` Informs all of my registered cursors that the specified element was just removed from my list.
`CursorableLinkedList.Cursor` | `cursor()` Returns a `CursorableLinkedList.Cursor` for iterating through the elements of this list.
`CursorableLinkedList.Cursor` | `cursor(int fromIndex)` Returns a `CursorableLinkedList.Cursor` for iterating through the elements of this list starting from a specified index.
`protected void` | `init()` The equivalent of a default constructor called by any constructor and by `readObject`.
`Iterator` | `iterator()` Returns an iterator that does not support concurrent modification.
`ListIterator` | `listIterator()` Returns a cursor iterator that allows changes to the underlying list in parallel.
`ListIterator` | `listIterator(int fromIndex)` Returns a cursor iterator that allows changes to the underlying list in parallel.
`protected void` | `registerCursor(CursorableLinkedList.Cursor cursor)` Registers a cursor to be notified of changes to this list.
`protected void` | `removeAllNodes()` Removes all nodes by iteration.
`protected void` | `removeNode(AbstractLinkedList.Node node)` Removes the specified node from the list.
`protected void` | `unregisterCursor(CursorableLinkedList.Cursor cursor)` Deregisters a cursor from the list to be notified of changes.
`protected void` | `updateNode(AbstractLinkedList.Node node, Object value)` Updates the node with a new value.

Methods inherited from class org.apache.commons.collections.list.AbstractLinkedList
`add, add, addAll, addAll, addFirst, addLast, addNodeAfter, addNodeBefore, clear, contains, containsAll, createHeaderNode, createNode, createSubListIterator, createSubListListIterator, doReadObject, doWriteObject, equals, get, getFirst, getLast, getNode, hashCode, indexOf, isEmpty, isEqualValue, lastIndexOf, remove, remove, removeAll, removeFirst, removeLast, retainAll, set, size, subList, toArray, toArray, toString`

Methods inherited from class java.lang.Object
`clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

Field Detail

### cursors

    protected transient List cursors

  A list of the cursor currently open on this list

Constructor Detail

### CursorableLinkedList

    public CursorableLinkedList()

  Constructor that creates.

### CursorableLinkedList

    public CursorableLinkedList(Collection coll)

  Constructor that copies the specified collection

Parameters:
  `coll` - the collection to copy

Method Detail

### 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 `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

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