org.apache.commons.collections.iterators
Class LoopingListIterator
- Iterator, ListIterator, ResettableIterator, ResettableListIterator
public class LoopingListIterator
A ListIterator that restarts when it reaches the end or when it
reaches the beginning.
The iterator will loop continuously around the provided list,
unless there are no elements in the collection to begin with, or
all of the elements have been
removed
.
Concurrent modifications are not directly supported, and for most
collection implementations will throw a
ConcurrentModificationException.
$Revision: 405920 $ $Date: 2006-05-12 23:48:04 +0100 (Fri, 12 May 2006) $
void | add(Object obj) - Inserts the specified element into the underlying list.
|
boolean | hasNext() - Returns whether this iterator has any more elements.
|
boolean | hasPrevious() - Returns whether this iterator has any more previous elements.
|
Object | next() - Returns the next object in the list.
|
int | nextIndex() - Returns the index of the element that would be returned by a
subsequent call to
next() .
|
Object | previous() - Returns the previous object in the list.
|
int | previousIndex() - Returns the index of the element that would be returned by a
subsequent call to
previous() .
|
void | remove() - Removes the previously retrieved item from the underlying list.
|
void | reset() - Resets the iterator back to the start of the list.
|
void | set(Object obj) - Replaces the last element that was returned by
next() or
previous() .
|
int | size() - Gets the size of the list underlying the iterator.
|
LoopingListIterator
public LoopingListIterator(List list)
Constructor that wraps a list.
There is no way to reset a ListIterator instance without
recreating it from the original source, so the List must be
passed in and a reference to it held.
add
public void add(Object obj)
Inserts the specified element into the underlying list.
The element is inserted before the next element that would be
returned by
next()
, if any, and after the next element
that would be returned by
previous()
, if any.
This feature is only supported if the underlying list's
List.listIterator
method returns an implementation
that supports it.
obj
- the element to insert
hasNext
public boolean hasNext()
Returns whether this iterator has any more elements.
Returns false only if the list originally had zero elements, or
all elements have been
removed
.
true
if there are more elements
hasPrevious
public boolean hasPrevious()
Returns whether this iterator has any more previous elements.
Returns false only if the list originally had zero elements, or
all elements have been
removed
.
true
if there are more elements
next
public Object next()
Returns the next object in the list.
If at the end of the list, returns the first element.
- the object after the last element returned
nextIndex
public int nextIndex()
Returns the index of the element that would be returned by a
subsequent call to
next()
.
As would be expected, if the iterator is at the physical end of
the underlying list, 0 is returned, signifying the beginning of
the list.
- the index of the element that would be returned if next() were called
previous
public Object previous()
Returns the previous object in the list.
If at the beginning of the list, return the last element. Note
that in this case, traversal to find that element takes linear time.
- the object before the last element returned
previousIndex
public int previousIndex()
Returns the index of the element that would be returned by a
subsequent call to
previous()
.
As would be expected, if at the iterator is at the physical
beginning of the underlying list, the list's size minus one is
returned, signifying the end of the list.
- the index of the element that would be returned if previous() were called
remove
public void remove()
Removes the previously retrieved item from the underlying list.
This feature is only supported if the underlying list's
iterator
method returns an implementation
that supports it.
This method can only be called after at least one
next()
or
previous()
method call. After a removal, the remove
method may not be called again until another
next()
or
previous()
has been performed. If the
reset()
is
called, then remove may not be called until
next()
or
previous()
is called again.
set
public void set(Object obj)
Replaces the last element that was returned by
next()
or
previous()
.
This feature is only supported if the underlying list's
List.listIterator
method returns an implementation
that supports it.
obj
- the element with which to replace the last element returned
size
public int size()
Gets the size of the list underlying the iterator.
Copyright © 2001-2009 Apache Software Foundation. All Rights Reserved.