org.apache.commons.collections4.iterators

Class LoopingIterator<E>

java.lang.Object

org.apache.commons.collections4.iterators.LoopingIterator<E>

All Implemented Interfaces:

java.util.Iterator<E>, ResettableIterator<E>

public class LoopingIterator<E>
extends java.lang.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:

3.0

Constructor Summary

Constructors

Constructor and Description
LoopingIterator(java.util.Collection<? extends E> coll) Constructor that wraps a collection.

Method Summary

Modifier and Type	Method and Description
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

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.util.Iterator

forEachRemaining

Constructor Detail

LoopingIterator

public LoopingIterator(java.util.Collection<? extends 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:

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<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 java.util.Iterator<E>

Returns:

the next object

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<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