Module java.base

Package java.util

Interface ListIterator<E>

Type Parameters:

E - the type of elements returned by this list iterator

All Superinterfaces:

Iterator<E>

public interface ListIterator<E>
extends Iterator<E>

An iterator for lists that allows the programmer to traverse the list in either direction, modify the list during iteration, and obtain the iterator's current position in the list. A ListIterator has no current element; its cursor position always lies between the element that would be returned by a call to previous() and the element that would be returned by a call to next(). An iterator for a list of length n has n+1 possible cursor positions, as illustrated by the carets (^) below:

                      Element(0)   Element(1)   Element(2)   ... Element(n-1)
 cursor positions:  ^            ^            ^            ^                  ^
 

Note that the remove() and set(Object) methods are not defined in terms of the cursor position; they are defined to operate on the last element returned by a call to next() or previous().

This interface is a member of the Java Collections Framework.

Since:

1.2

See Also:

• Collection
• List
• Iterator
• Enumeration
• List.listIterator()

Method Summary

Modifier and Type	Method	Description
void	add(E e)	Inserts the specified element into the list (optional operation).
boolean	hasNext()	Returns true if this list iterator has more elements when traversing the list in the forward direction.
boolean	hasPrevious()	Returns true if this list iterator has more elements when traversing the list in the reverse direction.
E	next()	Returns the next element in the list and advances the cursor position.
int	nextIndex()	Returns the index of the element that would be returned by a subsequent call to next().
E	previous()	Returns the previous element in the list and moves the cursor position backwards.
int	previousIndex()	Returns the index of the element that would be returned by a subsequent call to previous().
void	remove()	Removes from the list the last element that was returned by next() or previous() (optional operation).
void	set(E e)	Replaces the last element returned by next() or previous() with the specified element (optional operation).

Methods declared in interface java.util.Iterator

forEachRemaining

Method Details

hasNext

boolean hasNext()

Returns true if this list iterator has more elements when traversing the list in the forward direction. (In other words, returns true if next() would return an element rather than throwing an exception.)

Specified by:

hasNext in interface Iterator<E>

Returns:

true if the list iterator has more elements when traversing the list in the forward direction

next

E next()

Returns the next element in the list and advances the cursor position. This method may be called repeatedly to iterate through the list, or intermixed with calls to previous() to go back and forth. (Note that alternating calls to next and previous will return the same element repeatedly.)

Specified by:

next in interface Iterator<E>

Returns:

the next element in the list

Throws:

NoSuchElementException - if the iteration has no next element

hasPrevious

boolean hasPrevious()

Returns true if this list iterator has more elements when traversing the list in the reverse direction. (In other words, returns true if previous() would return an element rather than throwing an exception.)

Returns:

true if the list iterator has more elements when traversing the list in the reverse direction

previous

E previous()

Returns the previous element in the list and moves the cursor position backwards. This method may be called repeatedly to iterate through the list backwards, or intermixed with calls to next() to go back and forth. (Note that alternating calls to next and previous will return the same element repeatedly.)

Returns:

the previous element in the list

Throws:

NoSuchElementException - if the iteration has no previous element

nextIndex

int nextIndex()

Returns the index of the element that would be returned by a subsequent call to next(). (Returns list size if the list iterator is at the end of the list.)

Returns:

the index of the element that would be returned by a subsequent call to next, or list size if the list iterator is at the end of the list

previousIndex

int previousIndex()

Returns the index of the element that would be returned by a subsequent call to previous(). (Returns -1 if the list iterator is at the beginning of the list.)

Returns:

the index of the element that would be returned by a subsequent call to previous, or -1 if the list iterator is at the beginning of the list

remove

void remove()

Removes from the list the last element that was returned by next() or previous() (optional operation). This call can only be made once per call to next or previous. It can be made only if add(E) has not been called after the last call to next or previous.

Specified by:

remove in interface Iterator<E>

Throws:

UnsupportedOperationException - if the remove operation is not supported by this list iterator

IllegalStateException - if neither next nor previous have been called, or remove or add have been called after the last call to next or previous

set

void set(E e)

Replaces the last element returned by next() or previous() with the specified element (optional operation). This call can be made only if neither remove() nor add(E) have been called after the last call to next or previous.

Parameters:

e - the element with which to replace the last element returned by next or previous

Throws:

UnsupportedOperationException - if the set operation is not supported by this list iterator

ClassCastException - if the class of the specified element prevents it from being added to this list

IllegalArgumentException - if some aspect of the specified element prevents it from being added to this list

IllegalStateException - if neither next nor previous have been called, or remove or add have been called after the last call to next or previous

add

void add(E e)

Inserts the specified element into the list (optional operation). The element is inserted immediately before the element that would be returned by next(), if any, and after the element that would be returned by previous(), if any. (If the list contains no elements, the new element becomes the sole element on the list.) The new element is inserted before the implicit cursor: a subsequent call to next would be unaffected, and a subsequent call to previous would return the new element. (This call increases by one the value that would be returned by a call to nextIndex or previousIndex.)

Parameters:

e - the element to insert

Throws:

UnsupportedOperationException - if the add method is not supported by this list iterator

ClassCastException - if the class of the specified element prevents it from being added to this list

IllegalArgumentException - if some aspect of this element prevents it from being added to this list