/**
 * A Quack of objects
 *
 * This implementation uses linked memory
 *
 * @version 1.0
 * @author  Prof. David Bernstein, James Madison University
 */
    public class Quack
   {
      private Node first, last;
   
   
    /**
     * Construct a new (empty) Quack
     */
       public Quack()
      {
         first = null;
         last  = null;
      }
   
   
   
   
    /**
     * Pep an Object off of this Quack
     *
     * @return  The Object
     */
       public Object pep()
      {
         Node    temp;
         Object  value;
         value = null;
      
         if (first != null) 
         {
            value = first.value;
            if (first == last)
            {
               first = null;
            }
            else
            {
               temp  = last;
               while (temp.next != first)
               {
                  temp = temp.next;
               }
               first = temp;
               first.next = null;
            }
         } 
      
         if (first == null) last = null;
      
         return value;
      }
   
   
   
   
   
   
    /**
     * Pip an Object off of this Quack
     *
     * @return  The Object
     */
       public Object pip()
      {
         Object  value;
      
      
         if (last != null) 
         {
            value = last.value;
            last = last.next;
         } 
         else
         {
            value = null;
         }
         if (last == null) first = null;
      
         return value;
      }
   
   
   
   
   
   
   
   
    /**
     * Push an Object onto this Quack
     *
     * @param anObject   The Object to push
     */
       public void push(Object anObject)
      {
         Node temp;
      
         temp = new Node();
      
         temp.value = anObject;
         temp.next = last;
      
         last = temp;
         if (first == null) first = last;
      }
   }