Package org.apache.commons.collections4.iterators

Class LoopingIterator<E>

java.lang.Object
org.apache.commons.collections4.iterators.LoopingIterator<E>
Type Parameters:
E - the type of elements returned by this iterator.
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:
3.0

  • Constructor Summary

    Constructors
    Constructor
    Description
    LoopingIterator(Collection<? extends E> collection)
    Constructor that wraps a collection.

  • Method Summary

    Modifier and Type
    Method
    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

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

    Methods inherited from interface java.util.Iterator

    forEachRemaining

  • Constructor Details

    • LoopingIterator

      public LoopingIterator(Collection<? extends E> collection)
      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:
      collection - the collection to wrap
      Throws:
      NullPointerException - if the collection is null

  • Method Details

    • 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>
      Returns:
      the next object
      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