Package org.apache.commons.collections.iterators

Class ListIteratorWrapper

java.lang.Object

org.apache.commons.collections.iterators.ListIteratorWrapper

All Implemented Interfaces:

Iterator, ListIterator, ResettableIterator, ResettableListIterator

public class ListIteratorWrapper
extends Object
implements ResettableListIterator

Converts an iterator into a list iterator by caching the returned entries.

The ListIterator interface has additional useful methods for navigation - previous() and the index methods. This class allows a regular Iterator to behave as a ListIterator. It achieves this by building a list internally of as the underlying iterator is traversed.

The optional operations of ListIterator are not supported.

This class implements ResettableListIterator from Commons Collections 3.2.

Since:

Commons Collections 2.1

Version:

$Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $

Field Summary

Fields

Modifier and Type	Field	Description
private int	currentIndex	The current index of this iterator.
private final Iterator	iterator	The underlying iterator being decorated.
private final List	list	The list being used to cache the iterator.
private static final String	UNSUPPORTED_OPERATION_MESSAGE	Message used when remove, set or add are called.
private int	wrappedIteratorIndex	The current index of the wrapped iterator.

Constructor Summary

Constructors

Constructor	Description
ListIteratorWrapper(Iterator iterator)	Constructs a new ListIteratorWrapper that will wrap the given iterator.

Method Summary

Modifier and Type	Method	Description
void	add(Object obj)	Throws UnsupportedOperationException.
boolean	hasNext()	Returns true if there are more elements in the iterator.
boolean	hasPrevious()	Returns true if there are previous elements in the iterator.
Object	next()	Returns the next element from the iterator.
int	nextIndex()	Returns in the index of the next element.
Object	previous()	Returns the the previous element.
int	previousIndex()	Returns the index of the previous element.
void	remove()	Throws UnsupportedOperationException.
void	reset()	Resets this iterator back to the position at which the iterator was created.
void	set(Object obj)	Throws UnsupportedOperationException.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.util.Iterator

forEachRemaining

Field Details

UNSUPPORTED_OPERATION_MESSAGE

private static final String UNSUPPORTED_OPERATION_MESSAGE

Message used when remove, set or add are called.

See Also:

• Constant Field Values

iterator

private final Iterator iterator

The underlying iterator being decorated.

list

private final List list

The list being used to cache the iterator.

currentIndex

private int currentIndex

The current index of this iterator.

wrappedIteratorIndex

private int wrappedIteratorIndex

The current index of the wrapped iterator.

Constructor Details

ListIteratorWrapper

public ListIteratorWrapper(Iterator iterator)

Constructs a new ListIteratorWrapper that will wrap the given iterator.

Parameters:

iterator - the iterator to wrap

Throws:

NullPointerException - if the iterator is null

Method Details

add

public void add(Object obj)
         throws UnsupportedOperationException

Throws UnsupportedOperationException.

Specified by:

add in interface ListIterator

Parameters:

obj - the object to add, ignored

Throws:

UnsupportedOperationException - always

hasNext

public boolean hasNext()

Returns true if there are more elements in the iterator.

Specified by:

hasNext in interface Iterator

Specified by:

hasNext in interface ListIterator

Returns:

true if there are more elements

hasPrevious

public boolean hasPrevious()

Returns true if there are previous elements in the iterator.

Specified by:

hasPrevious in interface ListIterator

Returns:

true if there are previous elements

next

public Object next()
            throws NoSuchElementException

Returns the next element from the iterator.

Specified by:

next in interface Iterator

Specified by:

next in interface ListIterator

Returns:

the next element from the iterator

Throws:

NoSuchElementException - if there are no more elements

nextIndex

public int nextIndex()

Returns in the index of the next element.

Specified by:

nextIndex in interface ListIterator

Returns:

the index of the next element

previous

public Object previous()
                throws NoSuchElementException

Returns the the previous element.

Specified by:

previous in interface ListIterator

Returns:

the previous element

Throws:

NoSuchElementException - if there are no previous elements

previousIndex

public int previousIndex()

Returns the index of the previous element.

Specified by:

previousIndex in interface ListIterator

Returns:

the index of the previous element

remove

public void remove()
            throws UnsupportedOperationException

Throws UnsupportedOperationException.

Specified by:

remove in interface Iterator

Specified by:

remove in interface ListIterator

Throws:

UnsupportedOperationException - always

set

public void set(Object obj)
         throws UnsupportedOperationException

Throws UnsupportedOperationException.

Specified by:

set in interface ListIterator

Parameters:

obj - the object to set, ignored

Throws:

UnsupportedOperationException - always

reset

public void reset()

Resets this iterator back to the position at which the iterator was created.

Specified by:

reset in interface ResettableIterator

Specified by:

reset in interface ResettableListIterator

Since:

Commons Collections 3.2