/* ListEnum.java */

package sortedlist;

import java.util.Enumeration;

/** The ListEnum class implements an Enumeration for Linked Lists.
 *  ListEnum objects are mutable. 
 * @author Kathy Yelick                                       */

public class ListEnum implements Enumeration {
  /**
   *  Creates a new enumeration for the elements linked with ListNodes 
   *  starting with l.  Requires that there are no cycles in the list.
   */
  public ListEnum( ListNode l ) {
    trav = l;
  }

  /**
   *  Tests if this enumeration contains more elements.
   *  @return true if this enumeration contains more elements; false otherwise
   */
  public boolean hasMoreElements() {
    return (trav != null);
  }

  /**
   *  Returns the next element of this enumeration.
   *  Modifies the enumeration to move the enumeration past the returned 
   *  element of the list. 
   * @return the next element of this enumeration.
   */
  public Object nextElement() {
    Object retItem = trav.item;
    trav = trav.next;
    return retItem;
  }


  private ListNode trav;  
}