Interface ListIterator<E>
- 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 |
boolean | hasPrevious() | Returns |
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 |
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 |
void | remove() | Removes from the list the last element that was returned by |
void | set(E e) | Replaces the last element returned by |
Methods declared in interface java.util.Iterator
forEachRemaining
Method Detail
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 interfaceIterator<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 interfaceIterator<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 interfaceIterator<E>
- Throws:
-
UnsupportedOperationException
- if theremove
operation is not supported by this list iterator -
IllegalStateException
- if neithernext
norprevious
have been called, orremove
oradd
have been called after the last call tonext
orprevious
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 bynext
orprevious
- Throws:
-
UnsupportedOperationException
- if theset
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 neithernext
norprevious
have been called, orremove
oradd
have been called after the last call tonext
orprevious
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 theadd
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