ListIterator

public interface ListIterator
implements Iterator<E>

java.util.ListIterator<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(java.lang.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:

Summary

Public methods
`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 methods

From interface java.util.Iterator

`default void`	`forEachRemaining(Consumer<? super E> action)` Performs the given action for each remaining element until all elements have been processed or the action throws an exception.
`abstract boolean`	`hasNext()` Returns `true` if the iteration has more elements.
`abstract E`	`next()` Returns the next element in the iteration.
`default void`	`remove()` Removes from the underlying collection the last element returned by this iterator (optional operation).

Public methods

add

Added in API level 1

 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`	`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

hasNext

Added in API level 1

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

hasPrevious

Added in API level 1

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

Added in API level 1

 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
`E`	the next element in the list

Throws
`NoSuchElementException`	if the iteration has no next element

nextIndex

Added in API level 1

 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
`int`	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

Added in API level 1

 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
`E`	the previous element in the list

Throws
`NoSuchElementException`	if the iteration has no previous element

previousIndex

Added in API level 1

 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
`int`	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

Added in API level 1

 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`

set

Added in API level 1

 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`	`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`