ListIterator (Java Platform SE 8 ) (original) (raw)

• All Superinterfaces:
  Iterator

public interface ListIterator
extends Iterator
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() orprevious().
This interface is a member of the Java Collections Framework.
Since:
1.2
See Also:
Collection, List, Iterator, Enumeration, List.listIterator()

• • Method Summary

  All Methods Instance Methods Abstract Methods

  Modifier and Type	Method	Description
  void	add(E 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 and advances the cursor position.
  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 and moves the cursor position backwards.
  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 e)	Replaces the last element returned by next() orprevious() with the specified element (optional operation).

     * ### Methods inherited from interface java.util.[Iterator](../../java/util/Iterator.html "interface in java.util")  
     `[forEachRemaining](../../java/util/Iterator.html#forEachRemaining-java.util.function.Consumer-)`

• • 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()](../../java/util/ListIterator.html#next--) would return an element rather than throwing an exception.)  
     Specified by:  
     `[hasNext](../../java/util/Iterator.html#hasNext--)` in interface `[Iterator](../../java/util/Iterator.html "interface in java.util")<[E](../../java/util/ListIterator.html "type parameter in ListIterator")>`  
     Returns:  
     `true` if the list iterator has more elements when traversing the list in the forward direction  
     * #### next  
     [E](../../java/util/ListIterator.html "type parameter in ListIterator") 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()](../../java/util/ListIterator.html#previous--) to go back and forth. (Note that alternating calls to `next` and `previous` will return the same element repeatedly.)  
     Specified by:  
     `[next](../../java/util/Iterator.html#next--)` in interface `[Iterator](../../java/util/Iterator.html "interface in java.util")<[E](../../java/util/ListIterator.html "type parameter in ListIterator")>`  
     Returns:  
     the next element in the list  
     Throws:  
     `[NoSuchElementException](../../java/util/NoSuchElementException.html "class in java.util")` \- 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()](../../java/util/ListIterator.html#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](../../java/util/ListIterator.html "type parameter in ListIterator") 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()](../../java/util/ListIterator.html#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](../../java/util/NoSuchElementException.html "class in java.util")` \- 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()](../../java/util/ListIterator.html#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()](../../java/util/ListIterator.html#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()](../../java/util/ListIterator.html#next--) or [previous()](../../java/util/ListIterator.html#previous--) (optional operation). This call can only be made once per call to `next` or `previous`. It can be made only if [add(E)](../../java/util/ListIterator.html#add-E-) has not been called after the last call to `next` or `previous`.  
     Specified by:  
     `[remove](../../java/util/Iterator.html#remove--)` in interface `[Iterator](../../java/util/Iterator.html "interface in java.util")<[E](../../java/util/ListIterator.html "type parameter in ListIterator")>`  
     Throws:  
     `[UnsupportedOperationException](../../java/lang/UnsupportedOperationException.html "class in java.lang")` \- if the `remove` operation is not supported by this list iterator  
     `[IllegalStateException](../../java/lang/IllegalStateException.html "class in java.lang")` \- if 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](../../java/util/ListIterator.html "type parameter in ListIterator") e)  
     Replaces the last element returned by [next()](../../java/util/ListIterator.html#next--) or[previous()](../../java/util/ListIterator.html#previous--) with the specified element (optional operation). This call can be made only if neither [remove()](../../java/util/ListIterator.html#remove--) nor [add(E)](../../java/util/ListIterator.html#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](../../java/lang/UnsupportedOperationException.html "class in java.lang")` \- if the `set` operation is not supported by this list iterator  
     `[ClassCastException](../../java/lang/ClassCastException.html "class in java.lang")` \- if the class of the specified element prevents it from being added to this list  
     `[IllegalArgumentException](../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if some aspect of the specified element prevents it from being added to this list  
     `[IllegalStateException](../../java/lang/IllegalStateException.html "class in java.lang")` \- 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](../../java/util/ListIterator.html "type parameter in ListIterator") e)  
     Inserts the specified element into the list (optional operation). The element is inserted immediately before the element that would be returned by [next()](../../java/util/ListIterator.html#next--), if any, and after the element that would be returned by [previous()](../../java/util/ListIterator.html#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](../../java/lang/UnsupportedOperationException.html "class in java.lang")` \- if the `add` method is not supported by this list iterator  
     `[ClassCastException](../../java/lang/ClassCastException.html "class in java.lang")` \- if the class of the specified element prevents it from being added to this list  
     `[IllegalArgumentException](../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if some aspect of this element prevents it from being added to this list

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