Interface ListIterator<E>
- Type Parameters:
E
- the type of elements returned by this list iterator
- All Superinterfaces:
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:
-
Method Summary
Modifier and TypeMethodDescriptionvoid
Inserts the specified element into the list (optional operation).boolean
hasNext()
Returnstrue
if this list iterator has more elements when traversing the list in the forward direction.boolean
Returnstrue
if this list iterator has more elements when traversing the list in the reverse direction.next()
Returns the next element in the list and advances the cursor position.int
Returns the index of the element that would be returned by a subsequent call tonext()
.previous()
Returns the previous element in the list and moves the cursor position backwards.int
Returns the index of the element that would be returned by a subsequent call toprevious()
.void
remove()
Removes from the list the last element that was returned bynext()
orprevious()
(optional operation).void
Replaces the last element returned bynext()
orprevious()
with the specified element (optional operation).Methods declared in interface java.util.Iterator
forEachRemaining
-
Method Details
-
hasNext
boolean hasNext()Returnstrue
if this list iterator has more elements when traversing the list in the forward direction. (In other words, returnstrue
ifnext()
would return an element rather than throwing an exception.) -
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 toprevious()
to go back and forth. (Note that alternating calls tonext
andprevious
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()Returnstrue
if this list iterator has more elements when traversing the list in the reverse direction. (In other words, returnstrue
ifprevious()
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 tonext()
to go back and forth. (Note that alternating calls tonext
andprevious
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 tonext()
. (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 toprevious()
. (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 bynext()
orprevious()
(optional operation). This call can only be made once per call tonext
orprevious
. It can be made only ifadd(E)
has not been called after the last call tonext
orprevious
.- Specified by:
remove
in interfaceIterator<E>
- Throws:
UnsupportedOperationException
- if theremove
operation is not supported by this list iteratorIllegalStateException
- if neithernext
norprevious
have been called, orremove
oradd
have been called after the last call tonext
orprevious
-
set
Replaces the last element returned bynext()
orprevious()
with the specified element (optional operation). This call can be made only if neitherremove()
noradd(E)
have been called after the last call tonext
orprevious
.- 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 iteratorClassCastException
- if the class of the specified element prevents it from being added to this listIllegalArgumentException
- if some aspect of the specified element prevents it from being added to this listIllegalStateException
- if neithernext
norprevious
have been called, orremove
oradd
have been called after the last call tonext
orprevious
-
add
Inserts the specified element into the list (optional operation). The element is inserted immediately before the element that would be returned bynext()
, if any, and after the element that would be returned byprevious()
, 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 tonext
would be unaffected, and a subsequent call toprevious
would return the new element. (This call increases by one the value that would be returned by a call tonextIndex
orpreviousIndex
.)- Parameters:
e
- the element to insert- Throws:
UnsupportedOperationException
- if theadd
method is not supported by this list iteratorClassCastException
- if the class of the specified element prevents it from being added to this listIllegalArgumentException
- if some aspect of this element prevents it from being added to this list
-