org.apache.commons.collections

Class CursorableLinkedList

Implemented Interfaces:
List, Serializable

public class CursorableLinkedList
extends java.lang.Object
implements List, Serializable

A doubly-linked list implementation of the List interface, supporting a ListIterator that allows concurrent modifications to the underlying list.

Implements all of the optional List operations, the stack/queue/dequeue operations available in java.util.LinkedList and supports a ListIterator that allows concurrent modifications to the underlying list (see cursor).

Note that this implementation is not synchronized.

Version:
$Revision: 1.23 $ $Date: 2004/02/18 01:15:42 $
Authors:
Rodney Waldhoff
Janek Bogucki
Simon Kitching
Since:
Commons Collections 1.0
See Also:
java.util.LinkedList

Nested Class Summary

class
CursorableLinkedList.Cursor

Field Summary

protected List
_cursors
A list of the currently CursorableLinkedList.Cursors currently open in this list.
protected org.apache.commons.collections.CursorableLinkedList.Listable
_head
A sentry node.
protected int
_modCount
Tracks the number of structural modifications to me.
protected int
_size
The number of elements in me.

Method Summary

boolean
add(Object o)
Appends the specified element to the end of this list.
void
add(int index, Object element)
Inserts the specified element at the specified position in this list.
boolean
addAll(Collection c)
Appends all of the elements in the specified collection to the end of this list, in the order that they are returned by the specified Collection's Iterator.
boolean
addAll(int index, Collection c)
Inserts all of the elements in the specified collection into this list at the specified position.
boolean
addFirst(Object o)
Inserts the specified element at the beginning of this list.
boolean
addLast(Object o)
Inserts the specified element at the end of this list.
protected void
broadcastListableChanged(org.apache.commons.collections.CursorableLinkedList.Listable elt)
Informs all of my registered cursors that the specified element was changed.
protected void
broadcastListableInserted(org.apache.commons.collections.CursorableLinkedList.Listable elt)
Informs all of my registered cursors that the specified element was just added to my list.
protected void
broadcastListableRemoved(org.apache.commons.collections.CursorableLinkedList.Listable elt)
Informs all of my registered cursors that the specified element was just removed from my list.
void
clear()
Removes all of the elements from this list.
boolean
contains(Object o)
Returns true if this list contains the specified element.
boolean
containsAll(Collection c)
Returns true if this list contains all of the elements of the specified collection.
CursorableLinkedList.Cursor
cursor()
Returns a ListIterator for iterating through the elements of this list.
CursorableLinkedList.Cursor
cursor(int i)
Returns a ListIterator for iterating through the elements of this list, initialized such that ListIterator.next will return the element at the specified index (if any) and ListIterator.previous will return the element immediately preceding it (if any).
boolean
equals(Object o)
Compares the specified object with this list for equality.
Object
get(int index)
Returns the element at the specified position in this list.
Object
getFirst()
Returns the element at the beginning of this list.
Object
getLast()
Returns the element at the end of this list.
protected org.apache.commons.collections.CursorableLinkedList.Listable
getListableAt(int index)
Returns the org.apache.commons.collections.CursorableLinkedList.Listable at the specified index.
int
hashCode()
Returns the hash code value for this list.
int
indexOf(Object o)
Returns the index in this list of the first occurrence of the specified element, or -1 if this list does not contain this element.
protected org.apache.commons.collections.CursorableLinkedList.Listable
insertListable(org.apache.commons.collections.CursorableLinkedList.Listable before, org.apache.commons.collections.CursorableLinkedList.Listable after, Object value)
Inserts a new value into my list, after the specified before element, and before the specified after element
protected void
invalidateCursors()
Informs all of my registered cursors that they are now invalid.
boolean
isEmpty()
Returns true if this list contains no elements.
Iterator
iterator()
Returns a fail-fast iterator.
int
lastIndexOf(Object o)
Returns the index in this list of the last occurrence of the specified element, or -1 if this list does not contain this element.
ListIterator
listIterator()
Returns a fail-fast ListIterator.
ListIterator
listIterator(int index)
Returns a fail-fast ListIterator.
protected void
registerCursor(CursorableLinkedList.Cursor cur)
Registers a CursorableLinkedList.Cursor to be notified of changes to this list.
boolean
remove(Object o)
Removes the first occurrence in this list of the specified element.
Object
remove(int index)
Removes the element at the specified position in this list (optional operation).
boolean
removeAll(Collection c)
Removes from this list all the elements that are contained in the specified collection.
Object
removeFirst()
Removes the first element of this list, if any.
Object
removeLast()
Removes the last element of this list, if any.
protected void
removeListable(org.apache.commons.collections.CursorableLinkedList.Listable elt)
Removes the given org.apache.commons.collections.CursorableLinkedList.Listable from my list.
boolean
retainAll(Collection c)
Retains only the elements in this list that are contained in the specified collection.
Object
set(int index, Object element)
Replaces the element at the specified position in this list with the specified element.
int
size()
Returns the number of elements in this list.
List
subList(int i, int j)
Returns a fail-fast sublist.
Object[]
toArray()
Returns an array containing all of the elements in this list in proper sequence.
Object[]
toArray(a[] )
Returns an array containing all of the elements in this list in proper sequence; the runtime type of the returned array is that of the specified array.
String
toString()
Returns a String representation of this list, suitable for debugging.
protected void
unregisterCursor(CursorableLinkedList.Cursor cur)
Removes a CursorableLinkedList.Cursor from the set of cursors to be notified of changes to this list.

Field Details

_cursors

protected List _cursors

_head

protected org.apache.commons.collections.CursorableLinkedList.Listable _head
A sentry node.

_head.next() points to the first element in the list, _head.prev() to the last. Note that it is possible for _head.next().prev() and _head.prev().next() to be non-null, as when I am a sublist for some larger list. Use == _head.next() and == _head.prev() to determine if a given org.apache.commons.collections.CursorableLinkedList.Listable is the first or last element in the list.


_modCount

protected int _modCount
Tracks the number of structural modifications to me.

_size

protected int _size
The number of elements in me.

Method Details

add

public boolean add(Object o)
Appends the specified element to the end of this list.
Parameters:
o - element to be appended to this list.
Returns:
true

add

public void add(int index,
                Object element)
Inserts the specified element at the specified position in this list. Shifts the element currently at that position (if any) and any subsequent elements to the right (adds one to their indices).
Parameters:
index - index at which the specified element is to be inserted.
element - element to be inserted.

addAll

public boolean addAll(Collection c)
Appends all of the elements in the specified collection to the end of this list, in the order that they are returned by the specified Collection's Iterator. The behavior of this operation is unspecified if the specified collection is modified while the operation is in progress. (Note that this will occur if the specified collection is this list, and it's nonempty.)
Parameters:
c - collection whose elements are to be added to this list.
Returns:
true if this list changed as a result of the call.

addAll

public boolean addAll(int index,
                      Collection c)
Inserts all of the elements in the specified collection into this list at the specified position. Shifts the element currently at that position (if any) and any subsequent elements to the right (increases their indices). The new elements will appear in this list in the order that they are returned by the specified Collection's Iterator. The behavior of this operation is unspecified if the specified collection is modified while the operation is in progress. (Note that this will occur if the specified collection is this list, and it's nonempty.)
Parameters:
index - index at which to insert first element from the specified collection.
c - elements to be inserted into this list.
Returns:
true if this list changed as a result of the call.

addFirst

public boolean addFirst(Object o)
Inserts the specified element at the beginning of this list. (Equivalent to add(0,o)).
Parameters:
o - element to be prepended to this list.
Returns:
true

addLast

public boolean addLast(Object o)
Inserts the specified element at the end of this list. (Equivalent to add(java.lang.Object)).
Parameters:
o - element to be appended to this list.
Returns:
true

broadcastListableChanged

protected void broadcastListableChanged(org.apache.commons.collections.CursorableLinkedList.Listable elt)
Informs all of my registered cursors that the specified element was changed.
See Also:
set(int,java.lang.Object)

broadcastListableInserted

protected void broadcastListableInserted(org.apache.commons.collections.CursorableLinkedList.Listable elt)
Informs all of my registered cursors that the specified element was just added to my list.

broadcastListableRemoved

protected void broadcastListableRemoved(org.apache.commons.collections.CursorableLinkedList.Listable elt)
Informs all of my registered cursors that the specified element was just removed from my list.

clear

public void clear()
Removes all of the elements from this list. This list will be empty after this call returns (unless it throws an exception).

contains

public boolean contains(Object o)
Returns true if this list contains the specified element. More formally, returns true if and only if this list contains at least one element e such that (o==null ? e==null : o.equals(e)).
Parameters:
o - element whose presence in this list is to be tested.
Returns:
true if this list contains the specified element.

containsAll

public boolean containsAll(Collection c)
Returns true if this list contains all of the elements of the specified collection.
Parameters:
c - collection to be checked for containment in this list.
Returns:
true if this list contains all of the elements of the specified collection.

cursor

public CursorableLinkedList.Cursor cursor()
Returns a ListIterator for iterating through the elements of this list. Unlike iterator(), a cursor is not bothered by concurrent modifications to the underlying list.

Specifically, when elements are added to the list before or after the cursor, the cursor simply picks them up automatically. 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--i.e., it cannot be removed).

Note that the returned ListIterator does not support the ListIterator.nextIndex and ListIterator.previousIndex methods (they throw UnsupportedOperationException when invoked.

Historical Note: In previous versions of this class, the object returned from this method was required to be explicitly closed. This is no longer necessary.


cursor

public CursorableLinkedList.Cursor cursor(int i)
Returns a ListIterator for iterating through the elements of this list, initialized such that ListIterator.next will return the element at the specified index (if any) and ListIterator.previous will return the element immediately preceding it (if any). Unlike iterator(), a cursor is not bothered by concurrent modifications to the underlying list.

equals

public boolean equals(Object o)
Compares the specified object with this list for equality. Returns true if and only if the specified object is also a list, both lists have the same size, and all corresponding pairs of elements in the two lists are equal. (Two elements e1 and e2 are equal if (e1==null ? e2==null : e1.equals(e2)).) In other words, two lists are defined to be equal if they contain the same elements in the same order. This definition ensures that the equals method works properly across different implementations of the List interface.
Parameters:
o - the object to be compared for equality with this list.
Returns:
true if the specified object is equal to this list.

get

public Object get(int index)
Returns the element at the specified position in this list.
Parameters:
index - index of element to return.
Returns:
the element at the specified position in this list.

getFirst

public Object getFirst()
Returns the element at the beginning of this list.

getLast

public Object getLast()
Returns the element at the end of this list.

getListableAt

protected org.apache.commons.collections.CursorableLinkedList.Listable getListableAt(int index)
Returns the org.apache.commons.collections.CursorableLinkedList.Listable at the specified index.

hashCode

public int hashCode()
Returns the hash code value for this list. The hash code of a list is defined to be the result of the following calculation:
  hashCode = 1;
  Iterator i = list.iterator();
  while (i.hasNext()) {
      Object obj = i.next();
      hashCode = 31*hashCode + (obj==null ? 0 : obj.hashCode());
  }
 
This ensures that list1.equals(list2) implies that list1.hashCode()==list2.hashCode() for any two lists, list1 and list2, as required by the general contract of Object.hashCode.
Returns:
the hash code value for this list.

indexOf

public int indexOf(Object o)
Returns the index in this list of the first occurrence of the specified element, or -1 if this list does not contain this element. More formally, returns the lowest index i such that (o==null ? get(i)==null : o.equals(get(i))), or -1 if there is no such index.
Parameters:
o - element to search for.
Returns:
the index in this list of the first occurrence of the specified element, or -1 if this list does not contain this element.

insertListable

protected org.apache.commons.collections.CursorableLinkedList.Listable insertListable(org.apache.commons.collections.CursorableLinkedList.Listable before,
                                                                                      org.apache.commons.collections.CursorableLinkedList.Listable after,
                                                                                      Object value)
Inserts a new value into my list, after the specified before element, and before the specified after element
Returns:
the newly created org.apache.commons.collections.CursorableLinkedList.Listable

invalidateCursors

protected void invalidateCursors()
Informs all of my registered cursors that they are now invalid.

isEmpty

public boolean isEmpty()
Returns true if this list contains no elements.
Returns:
true if this list contains no elements.

iterator

public Iterator iterator()
Returns a fail-fast iterator.
See Also:
List.iterator

lastIndexOf

public int lastIndexOf(Object o)
Returns the index in this list of the last occurrence of the specified element, or -1 if this list does not contain this element. More formally, returns the highest index i such that (o==null ? get(i)==null : o.equals(get(i))), or -1 if there is no such index.
Parameters:
o - element to search for.
Returns:
the index in this list of the last occurrence of the specified element, or -1 if this list does not contain this element.

listIterator

public ListIterator listIterator()
Returns a fail-fast ListIterator.
See Also:
List.listIterator

listIterator

public ListIterator listIterator(int index)
Returns a fail-fast ListIterator.
See Also:
List.listIterator(int)

registerCursor

protected void registerCursor(CursorableLinkedList.Cursor cur)
Registers a CursorableLinkedList.Cursor to be notified of changes to this list.

remove

public boolean remove(Object o)
Removes the first occurrence in this list of the specified element. If this list does not contain the element, it is unchanged. More formally, removes the element with the lowest index i such that (o==null ? get(i)==null : o.equals(get(i))) (if such an element exists).
Parameters:
o - element to be removed from this list, if present.
Returns:
true if this list contained the specified element.

remove

public Object remove(int index)
Removes the element at the specified position in this list (optional operation). Shifts any subsequent elements to the left (subtracts one from their indices). Returns the element that was removed from the list.
Parameters:
index - the index of the element to removed.
Returns:
the element previously at the specified position.

removeAll

public boolean removeAll(Collection c)
Removes from this list all the elements that are contained in the specified collection.
Parameters:
c - collection that defines which elements will be removed from this list.
Returns:
true if this list changed as a result of the call.

removeFirst

public Object removeFirst()
Removes the first element of this list, if any.

removeLast

public Object removeLast()
Removes the last element of this list, if any.

removeListable

protected void removeListable(org.apache.commons.collections.CursorableLinkedList.Listable elt)
Removes the given org.apache.commons.collections.CursorableLinkedList.Listable from my list.

retainAll

public boolean retainAll(Collection c)
Retains only the elements in this list that are contained in the specified collection. In other words, removes from this list all the elements that are not contained in the specified collection.
Parameters:
c - collection that defines which elements this set will retain.
Returns:
true if this list changed as a result of the call.

set

public Object set(int index,
                  Object element)
Replaces the element at the specified position in this list with the specified element.
Parameters:
index - index of element to replace.
element - element to be stored at the specified position.
Returns:
the element previously at the specified position.

size

public int size()
Returns the number of elements in this list.
Returns:
the number of elements in this list.

subList

public List subList(int i,
                    int j)
Returns a fail-fast sublist.
See Also:
List.subList(int,int)

toArray

public Object[] toArray()
Returns an array containing all of the elements in this list in proper sequence. Obeys the general contract of the Collection.toArray method.
Returns:
an array containing all of the elements in this list in proper sequence.

toArray

public Object[] toArray(a[] )
Returns an array containing all of the elements in this list in proper sequence; the runtime type of the returned array is that of the specified array. Obeys the general contract of the Collection.toArray method.
Parameters:
Returns:
an array containing the elements of this list.

toString

public String toString()
Returns a String representation of this list, suitable for debugging.
Returns:
a String representation of this list, suitable for debugging.

unregisterCursor

protected void unregisterCursor(CursorableLinkedList.Cursor cur)
Removes a CursorableLinkedList.Cursor from the set of cursors to be notified of changes to this list.

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