Package java.util

Interface Iterator<E>

  • Type Parameters:
    E - the type of object returned by the iterator.
    All Known Subinterfaces:
    ListIterator<E>

    public interface Iterator<E>
    An iterator over a sequence of objects, such as a collection.

    If a collection has been changed since the iterator was created, methods next and hasNext() may throw a ConcurrentModificationException. It is not possible to guarantee that this mechanism works in all cases of unsynchronized concurrent modification. It should only be used for debugging purposes. Iterators with this behavior are called fail-fast iterators.

    Implementing Iterable and returning an Iterator allows your class to be used as a collection with the enhanced for loop.

    • Method Summary

      All Methods Instance Methods Abstract Methods 
      Modifier and Type Method Description
      boolean hasNext()
      Returns true if there is at least one more element, false otherwise.
      E next()
      Returns the next object and advances the iterator.
      void remove()
      Removes the last object returned by next from the collection.
    • Method Detail

      • hasNext

        boolean hasNext()
        Returns true if there is at least one more element, false otherwise.
        Returns:
        true if there is a next element.
        See Also:
        next()
      • next

        E next()
        Returns the next object and advances the iterator.
        Returns:
        the next object.
        Throws:
        java.util.NoSuchElementException - if there are no more elements.
        See Also:
        hasNext()
      • remove

        void remove()
        Removes the last object returned by next from the collection. This method can only be called once between each call to next.
        Throws:
        java.lang.UnsupportedOperationException - if removing is not supported by the collection being iterated.
        java.lang.IllegalStateException - if next has not been called, or remove has already been called after the last call to next.