Package org.apache.commons.collections4.iterators

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

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      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

        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