LoopingListIterator (Apache Commons Collections 4.0 API)

java.lang.Object
- org.apache.commons.collections4.iterators.LoopingListIterator<E>

All Implemented Interfaces:

Iterator<E>, ListIterator<E>, OrderedIterator<E>, ResettableIterator<E>, ResettableListIterator<E>
```
public class LoopingListIterator<E>
extends Object
implements ResettableListIterator<E>
```
A ListIterator that restarts when it reaches the end or when it reaches the beginning.
The iterator will loop continuously around the provided list, unless there are no elements in the collection to begin with, or all of the elements have been removed.
Concurrent modifications are not directly supported, and for most collection implementations will throw a ConcurrentModificationException.

Since:

3.2

Version:

$Id: LoopingListIterator.java 1494333 2013-06-18 21:59:21Z sebb $

Constructor Summary

Constructors
Constructor and Description

LoopingListIterator(List<E> list)
Constructor that wraps a list.

Constructors
Constructor and Description
`LoopingListIterator(List<E> list)` Constructor that wraps a list.

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`add(E obj)` Inserts the specified element into the underlying list.
`boolean`	`hasNext()` Returns whether this iterator has any more elements.
`boolean`	`hasPrevious()` Returns whether this iterator has any more previous elements.
`E`	`next()` Returns the next object 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 object in the list.
`int`	`previousIndex()` Returns the index of the element that would be returned by a subsequent call to `previous()`.
`void`	`remove()` Removes the previously retrieved item from the underlying list.
`void`	`reset()` Resets the iterator back to the start of the list.
`void`	`set(E obj)` Replaces the last element that was returned by `next()` or `previous()`.
`int`	`size()` Gets the size of the list underlying the iterator.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - LoopingListIterator
```
public LoopingListIterator(List<E> list)
```
    Constructor that wraps a list.
    There is no way to reset a ListIterator instance without recreating it from the original source, so the List must be passed in and a reference to it held.
    
    Parameters:
    list - the list to wrap
    
    Throws:
    
    NullPointerException - if the list it null
- Method Detail
  - hasNext
```
public boolean hasNext()
```
    Returns whether this iterator has any more elements.
    Returns false only if the list originally had zero elements, or all elements have been removed.
    
    Specified by:
    
    hasNext in interface Iterator<E>
    
    Specified by:
    
    hasNext in interface ListIterator<E>
    
    Returns:
    true if there are more elements
  - next
```
public E next()
```
    Returns the next object in the list.
    If at the end of the list, returns the first element.
    
    Specified by:
    
    next in interface Iterator<E>
    
    Specified by:
    
    next in interface ListIterator<E>
    
    Returns:
    the object after the last element returned
    
    Throws:
    
    NoSuchElementException - if there are no elements in the list
  - nextIndex
```
public int nextIndex()
```
    Returns the index of the element that would be returned by a subsequent call to next().
    As would be expected, if the iterator is at the physical end of the underlying list, 0 is returned, signifying the beginning of the list.
    
    Specified by:
    
    nextIndex in interface ListIterator<E>
    
    Returns:
    the index of the element that would be returned if next() were called
    
    Throws:
    
    NoSuchElementException - if there are no elements in the list
  - hasPrevious
```
public boolean hasPrevious()
```
    Returns whether this iterator has any more previous elements.
    Returns false only if the list originally had zero elements, or all elements have been removed.
    
    Specified by:
    
    hasPrevious in interface ListIterator<E>
    
    Specified by:
    
    hasPrevious in interface OrderedIterator<E>
    
    Returns:
    true if there are more elements
  - previous
```
public E previous()
```
    Returns the previous object in the list.
    If at the beginning of the list, return the last element. Note that in this case, traversal to find that element takes linear time.
    
    Specified by:
    
    previous in interface ListIterator<E>
    
    Specified by:
    
    previous in interface OrderedIterator<E>
    
    Returns:
    the object before the last element returned
    
    Throws:
    
    NoSuchElementException - if there are no elements in the list
  - previousIndex
```
public int previousIndex()
```
    Returns the index of the element that would be returned by a subsequent call to previous().
    As would be expected, if at the iterator is at the physical beginning of the underlying list, the list's size minus one is returned, signifying the end of the list.
    
    Specified by:
    
    previousIndex in interface ListIterator<E>
    
    Returns:
    the index of the element that would be returned if previous() were called
    
    Throws:
    
    NoSuchElementException - if there are no elements in the list
  - remove
```
public void remove()
```
    Removes the previously retrieved item from the underlying list.
    This feature is only supported if the underlying list's iterator method returns an implementation that supports it.
    This method can only be called after at least one next() or previous() method call. After a removal, the remove method may not be called again until another next() or previous() has been performed. If the reset() is called, then remove may not be called until next() or previous() is called again.
    
    Specified by:
    
    remove in interface Iterator<E>
    
    Specified by:
    
    remove in interface ListIterator<E>
    
    Throws:
    
    UnsupportedOperationException - if the remove method is not supported by the iterator implementation of the underlying list
  - add
```
public void add(E obj)
```
    Inserts the specified element into the underlying list.
    The element is inserted 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.
    This feature is only supported if the underlying list's List.listIterator() method returns an implementation that supports it.
    
    Specified by:
    
    add in interface ListIterator<E>
    
    Parameters:
    obj - the element to insert
    
    Throws:
    
    UnsupportedOperationException - if the add method is not supported by the iterator implementation of the underlying list
  - set
```
public void set(E obj)
```
    Replaces the last element that was returned by next() or previous().
    This feature is only supported if the underlying list's List.listIterator() method returns an implementation that supports it.
    
    Specified by:
    
    set in interface ListIterator<E>
    
    Parameters:
    obj - the element with which to replace the last element returned
    
    Throws:
    
    UnsupportedOperationException - if the set method is not supported by the iterator implementation of the underlying list
  - reset
```
public void reset()
```
    Resets the iterator back to the start of the list.
    
    Specified by:
    
    reset in interface ResettableIterator<E>
  - size
```
public int size()
```
    Gets the size of the list underlying the iterator.
    
    Returns:
    the current list size

Class LoopingListIterator<E>

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

LoopingListIterator

Method Detail

hasNext

next

nextIndex

hasPrevious

previous

previousIndex

remove

add

set

reset

size