import java.util.NoSuchElementException;

/**
 * Interface for iterator over ordered lists of objects.<br>
 * CSE 373 demonstration program, Winter 2006
 * @author Hal Perkins
 * @version 1/5/06
 */
public interface BasicListIterator {
  
  /**
   * Return true if this iteration has more elements in the forward direction
   * @return true if more elements are available, otherwise false
   */
  public boolean hasNext();
  
  /**
   * Return the next element in this iteration over the underlying collection
   * @return the next element in the iteration
   * @throws NoSuchElementException if the iteration has no more elements
   */
  public Object next() throws NoSuchElementException;

  /**
   * Return true if this iteration has more elements in the reverse direction
   * @return true if more elements are available, otherwise false
   */
  public boolean hasPrevious();
  
  /**
   * Return the previous element in this iteration over the underlying collection
   * @return the previous element in the iteration
   * @throws NoSuchElementException if the iteration has no more elements
   */
  public Object previous() throws NoSuchElementException;

  /**
   * Remove from the underlying collection the last element returned by
   * this iterator.  This can only be called once per call to next.
   * @throws IllegalStateException if next has not yet been called or if
   *         remove is called more than once after a call to next.
   */
  public void remove() throws IllegalStateException;
  
}