org.apache.commons.collections.iterators
Class LoopingIterator<E>

java.lang.Object
  extended by org.apache.commons.collections.iterators.LoopingIterator<E>
All Implemented Interfaces:
Iterator<E>, ResettableIterator<E>

public class LoopingIterator<E>
extends Object
implements ResettableIterator<E>

An Iterator that restarts when it reaches the end.

The iterator will loop continuously around the provided elements, unless there are no elements in the collection to begin with, or all the elements have been removed.

Concurrent modifications are not directly supported, and for most collection implementations will throw a ConcurrentModificationException.

Since:
Commons Collections 3.0
Version:
$Revision: 1.1.1.1 $ $Date: 2005/05/23 04:34:56 $
Author:
Jonathan Carlson, Matt Hall, John Watkinson, Stephen Colebourne

Constructor Summary
LoopingIterator(Collection<E> coll)
          Constructor that wraps a collection.
 
Method Summary
 boolean hasNext()
          Has the iterator any more elements.
 E next()
          Returns the next object in the collection.
 void remove()
          Removes the previously retrieved item from the underlying collection.
 void reset()
          Resets the iterator back to the start of the collection.
 int size()
          Gets the size of the collection underlying the iterator.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

LoopingIterator

public LoopingIterator(Collection<E> coll)
Constructor that wraps a collection.

There is no way to reset an Iterator instance without recreating it from the original source, so the Collection must be passed in.

Parameters:
coll - the collection to wrap
Throws:
NullPointerException - if the collection is null
Method Detail

hasNext

public boolean hasNext()
Has the iterator any more elements.

Returns false only if the collection originally had zero elements, or all the elements have been removed.

Specified by:
hasNext in interface Iterator<E>
Returns:
true if there are more elements

next

public E next()
Returns the next object in the collection.

If at the end of the collection, return the first element.

Specified by:
next in interface Iterator<E>
Throws:
NoSuchElementException - if there are no elements at all. Use hasNext() to avoid this error.

remove

public void remove()
Removes the previously retrieved item from the underlying collection.

This feature is only supported if the underlying collection's iterator method returns an implementation that supports it.

This method can only be called after at least one next() method call. After a removal, the remove method may not be called again until another next has been performed. If the reset() is called, then remove may not be called until next() is called again.

Specified by:
remove in interface Iterator<E>

reset

public void reset()
Resets the iterator back to the start of the collection.

Specified by:
reset in interface ResettableIterator<E>

size

public int size()
Gets the size of the collection underlying the iterator.

Returns:
the current collection size


Copyright © 2005-2005 Apache Software Foundation, Matt Hall, John Watkinson. All Rights Reserved.