Package org.apache.commons.collections4.iterators

Class ListIteratorWrapper<E>

java.lang.Object

org.apache.commons.collections4.iterators.ListIteratorWrapper<E>

Type Parameters:

E - the type of elements in this iterator.

All Implemented Interfaces:

Iterator<E>, ListIterator<E>, OrderedIterator<E>, ResettableIterator<E>, ResettableListIterator<E>

public class ListIteratorWrapper<E>
extends Object
implements ResettableListIterator<E>

Converts an Iterator into a ResettableListIterator. For plain Iterators this is accomplished by caching the returned elements. This class can also be used to simply add ResettableIterator functionality to a given ListIterator.

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 for plain Iterators.

This class implements ResettableListIterator from Commons Collections 3.2.

Since:

2.1

Constructor Summary

Constructors

Constructor	Description
ListIteratorWrapper(Iterator<? extends E> iterator)	Constructs a new ListIteratorWrapper that will wrap the given iterator.

Method Summary

Modifier and Type	Method	Description
void	add(E obj)	Throws UnsupportedOperationException unless the underlying Iterator is a ListIterator.
boolean	hasNext()	Returns true if there are more elements in the iterator.
boolean	hasPrevious()	Returns true if there are previous elements in the iterator.
E	next()	Returns the next element from the iterator.
int	nextIndex()	Returns the index of the next element.
E	previous()	Returns the previous element.
int	previousIndex()	Returns the index of the previous element.
void	remove()	Removes the last element that was returned by next() or previous() from the underlying collection.
void	reset()	Resets this iterator back to the position at which the iterator was created.
void	set(E obj)	Throws UnsupportedOperationException unless the underlying Iterator is a ListIterator.

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

Constructor Details

ListIteratorWrapper

public ListIteratorWrapper(Iterator<? extends E> 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(E obj)
         throws UnsupportedOperationException

Throws UnsupportedOperationException unless the underlying Iterator is a ListIterator.

Specified by:

add in interface ListIterator<E>

Parameters:

obj - the object to add

Throws:

UnsupportedOperationException - if the underlying iterator is not of type ListIterator

hasNext

public boolean hasNext()

Returns true if there are more elements in the iterator.

Specified by:

hasNext in interface Iterator<E>

Specified by:

hasNext in interface ListIterator<E>

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<E>

Specified by:

hasPrevious in interface OrderedIterator<E>

Returns:

true if there are previous elements

next

public E next()
       throws NoSuchElementException

Returns the next element from the iterator.

Specified by:

next in interface Iterator<E>

Specified by:

next in interface ListIterator<E>

Returns:

the next element from the iterator

Throws:

NoSuchElementException - if there are no more elements

nextIndex

public int nextIndex()

Returns the index of the next element.

Specified by:

nextIndex in interface ListIterator<E>

Returns:

the index of the next element

previous

public E previous()
           throws NoSuchElementException

Returns the previous element.

Specified by:

previous in interface ListIterator<E>

Specified by:

previous in interface OrderedIterator<E>

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<E>

Returns:

the index of the previous element

remove

public void remove()
            throws IllegalStateException

Removes the last element that was returned by next() or previous() from the underlying collection. This call can only be made once per call to next or previous and only if add(Object) was not called in between.

Specified by:

remove in interface Iterator<E>

Specified by:

remove in interface ListIterator<E>

Throws:

IllegalStateException - if next or previous have not been called before, or if remove or add have been called after the last call to next or previous

reset

public void reset()

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

Specified by:

reset in interface ResettableIterator<E>

Since:

3.2

set

public void set(E obj)
         throws UnsupportedOperationException

Throws UnsupportedOperationException unless the underlying Iterator is a ListIterator.

Specified by:

set in interface ListIterator<E>

Parameters:

obj - the object to set

Throws:

UnsupportedOperationException - if the underlying iterator is not of type ListIterator