org.apache.commons.collections4.iterators

Class 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:
    3.0

    • Constructor Summary

      Constructors

      Constructor and Description
      LoopingIterator(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.

    • Constructor Detail

      • LoopingIterator

        public LoopingIterator(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:
        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>
        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.

      • reset

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

      • size

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