java.util

Interface ListIterator

All Superinterfaces:

Iterator

public interface ListIterator
extends Iterator

An extended version of Iterator to support the extra features of Lists. The elements may be accessed in forward or reverse order, elements may be replaced as well as removed, and new elements may be inserted, during the traversal of the list.

A list with n elements provides n+1 iterator positions (the front, the end, or between two elements). Note that remove and set operate on the last element returned, whether it was by next or previous.

Since:

1.2

Author:

Original author unknown, Eric Blake

See Also:

Collection, List, Iterator, Enumeration

Method Summary

Modifier and Type	Method and Description
void	add(Object o) Insert an element into the list at the current position of the iterator (optional operation).
boolean	hasNext() Tests whether there are elements remaining in the list in the forward direction.
boolean	hasPrevious() Tests whether there are elements remaining in the list in the reverse direction.
Object	next() Obtain the next element in the list in the forward direction.
int	nextIndex() Find the index of the element that would be returned by a call to next.
Object	previous() Obtain the next element in the list in the reverse direction.
int	previousIndex() Find the index of the element that would be returned by a call to previous.
void	remove() Remove from the list the element last returned by a call to next or previous (optional operation).
void	set(Object o) Replace the element last returned by a call to next or previous with a given object (optional operation).

Method Detail

hasNext

boolean hasNext()

Tests whether there are elements remaining in the list in the forward direction. In other words, next() will not fail with a NoSuchElementException.

Specified by:

hasNext in interface Iterator

Returns:

true if the list continues in the forward direction

hasPrevious

boolean hasPrevious()

Tests whether there are elements remaining in the list in the reverse direction. In other words, previous() will not fail with a NoSuchElementException.

Returns:

true if the list continues in the reverse direction

next

Object next()

Obtain the next element in the list in the forward direction. Repeated calls to next may be used to iterate over the entire list, or calls to next and previous may be used together to go forwards and backwards. Alternating calls to next and previous will return the same element.

Specified by:

next in interface Iterator

Returns:

the next element in the list in the forward direction

Throws:

NoSuchElementException - if there are no more elements

previous

Object previous()

Obtain the next element in the list in the reverse direction. Repeated calls to previous may be used to iterate backwards over the entire list, or calls to next and previous may be used together to go forwards and backwards. Alternating calls to next and previous will return the same element.

Returns:

the next element in the list in the reverse direction

Throws:

NoSuchElementException - if there are no more elements

nextIndex

int nextIndex()

Find the index of the element that would be returned by a call to next. If hasNext() returns false, this returns the list size.

Returns:

the index of the element that would be returned by next()

previousIndex

int previousIndex()

Find the index of the element that would be returned by a call to previous. If hasPrevious() returns false, this returns -1.

Returns:

the index of the element that would be returned by previous()

add

void add(Object o)

Insert an element into the list at the current position of the iterator (optional operation). The element is inserted in between the element that would be returned by previous and the element that would be returned by next. After the insertion, a subsequent call to next is unaffected, but a call to previous returns the item that was added. The values returned by nextIndex() and previousIndex() are incremented.

Parameters:

o - the object to insert into the list

Throws:

ClassCastException - the object is of a type which cannot be added to this list

IllegalArgumentException - some other aspect of the object stops it being added to this list

UnsupportedOperationException - if this ListIterator does not support the add operation

remove

void remove()

Remove from the list the element last returned by a call to next or previous (optional operation). This method may only be called if neither add nor remove have been called since the last call to next or previous.

Specified by:

remove in interface Iterator

Throws:

IllegalStateException - if neither next or previous have been called, or if add or remove has been called since the last call to next or previous

UnsupportedOperationException - if this ListIterator does not support the remove operation

set

void set(Object o)

Replace the element last returned by a call to next or previous with a given object (optional operation). This method may only be called if neither add nor remove have been called since the last call to next or previous.

Parameters:

o - the object to replace the element with

Throws:

ClassCastException - the object is of a type which cannot be added to this list

IllegalArgumentException - some other aspect of the object stops it being added to this list

IllegalStateException - if neither next or previous have been called, or if add or remove has been called since the last call to next or previous

UnsupportedOperationException - if this ListIterator does not support the set operation