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java.util
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()
. In a list of length
n
, there are
n+1
valid index values, from
0
to
n
, inclusive.
Element(0) Element(1) Element(2) ... Element(n)
^ ^ ^ ^ ^
Index: 0 1 2 3 n+1
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
Method Summary
|
void |
add
(
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. |
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. |
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
Replaces the last element returned by
next
or
previous
with the specified element (optional operation). |
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. 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. 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 list iterator is at end of 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 list iterator is at beginning of 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
ListIterator.add
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
- 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) o)
-
Replaces the last element returned by
next
or
previous
with the specified element (optional operation). This call can be made only if neither
ListIterator.remove
nor
ListIterator.add
have been called after the last call to
next
or
previous
.
-
-
-
Parameters:
-
e
o
- 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) o)
-
Inserts the specified element into the list (optional operation). The element is inserted immediately before the next element that would be returned by
next
, if any, and after the next 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
o
- 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.