org.apache.commons.collections.iterators
Class LoopingIterator

java.lang.Object
  org.apache.commons.collections.iterators.LoopingIterator

All Implemented Interfaces:

java.util.Iterator, ResettableIterator

public class LoopingIterator
extends java.lang.Object
implements ResettableIterator

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: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $

Author:

Jonathan Carlson, Stephen Colebourne

Constructor Summary

LoopingIterator(java.util.Collection coll)
Constructor that wraps a collection.

Method Summary

boolean	hasNext() Has the iterator any more elements.
java.lang.Object	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(java.util.Collection 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:

java.lang.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 java.util.Iterator

Returns:

true if there are more elements

next

public java.lang.Object next()

Returns the next object in the collection.

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

Specified by:

next in interface java.util.Iterator

Throws:

java.util.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 java.util.Iterator

reset

public void reset()

Resets the iterator back to the start of the collection.

Specified by:

reset in interface ResettableIterator

size

public int size()

Gets the size of the collection underlying the iterator.

Returns:

the current collection size