ListIterator

public interface ListIterator implements 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.

See Also

Public Method Summary

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

Inherited Method Summary

Public Methods

public abstract 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

public abstract 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.)

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

public abstract 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

public abstract 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.)

Returns
  • the next element in the list
Throws
NoSuchElementException if the iteration has no next element

public abstract 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

public abstract 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

public abstract 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

public abstract 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.

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

public abstract 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