org.apache.commons.collections.list

Class CursorableLinkedList

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 java.util.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: 348013 $ $Date: 2005-11-21 23:24:45 +0000 (Mon, 21 Nov 2005) $

Author: Rodney Waldhoff Janek Bogucki Simon Kitching Stephen Colebourne

See Also: java.util.LinkedList

Nested Class Summary
static classCursorableLinkedList.Cursor
An extended ListIterator that allows concurrent changes to the underlying list.
protected static classCursorableLinkedList.SubCursor
A cursor for the sublist based on LinkedSubListIterator.
Field Summary
protected Listcursors
A list of the cursor currently open on this list
Constructor Summary
CursorableLinkedList()
Constructor that creates.
CursorableLinkedList(Collection coll)
Constructor that copies the specified collection
Method Summary
protected voidaddNode(Node nodeToInsert, Node insertBeforeNode)
Inserts a new node into the list.
protected voidbroadcastNodeChanged(Node node)
Informs all of my registered cursors that the specified element was changed.
protected voidbroadcastNodeInserted(Node node)
Informs all of my registered cursors that the specified element was just added to my list.
protected voidbroadcastNodeRemoved(Node node)
Informs all of my registered cursors that the specified element was just removed from my list.
protected ListIteratorcreateSubListListIterator(LinkedSubList subList, int fromIndex)
Creates a list iterator for the sublist.
CursorableLinkedList.Cursorcursor()
Returns a Cursor for iterating through the elements of this list.
CursorableLinkedList.Cursorcursor(int fromIndex)
Returns a Cursor for iterating through the elements of this list starting from a specified index.
protected voidinit()
The equivalent of a default constructor called by any constructor and by readObject.
Iteratoriterator()
Returns an iterator that does not support concurrent modification.
ListIteratorlistIterator()
Returns a cursor iterator that allows changes to the underlying list in parallel.
ListIteratorlistIterator(int fromIndex)
Returns a cursor iterator that allows changes to the underlying list in parallel.
protected voidregisterCursor(CursorableLinkedList.Cursor cursor)
Registers a cursor to be notified of changes to this list.
protected voidremoveAllNodes()
Removes all nodes by iteration.
protected voidremoveNode(Node node)
Removes the specified node from the list.
protected voidunregisterCursor(CursorableLinkedList.Cursor cursor)
Deregisters a cursor from the list to be notified of changes.
protected voidupdateNode(Node node, Object value)
Updates the node with a new value.

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

addNode

protected void addNode(Node nodeToInsert, Node insertBeforeNode)
Inserts a new node into the list.

Parameters: nodeToInsert new node to insert insertBeforeNode node to insert before

Throws: NullPointerException if either node is null

broadcastNodeChanged

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

Parameters: node the node that was changed

broadcastNodeInserted

protected void broadcastNodeInserted(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

broadcastNodeRemoved

protected void broadcastNodeRemoved(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

createSubListListIterator

protected ListIterator createSubListListIterator(LinkedSubList subList, int fromIndex)
Creates a list iterator for the sublist.

Parameters: subList the sublist to get an iterator for fromIndex the index to start from, relative to the sublist

cursor

public CursorableLinkedList.Cursor cursor()
Returns a 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 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 CursorableLinkedList 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.

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.

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).

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).

Parameters: fromIndex the index to start from

Returns: a new cursor iterator

registerCursor

protected void registerCursor(CursorableLinkedList.Cursor 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.

removeNode

protected void removeNode(Node node)
Removes the specified node from the list.

Parameters: node the node to remove

Throws: NullPointerException if node is null

unregisterCursor

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

Parameters: cursor the cursor to deregister

updateNode

protected void updateNode(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.

Parameters: node node to update value new value of the node

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