public class ListElem<KeyType, ValueType>       // ListElem has 2 parameters
{
   public  KeyType key; 
   public  ValueType value; 

   public  ListElem<KeyType,ValueType> prev;
   public  ListElem<KeyType,ValueType> next;

   public ListElem(KeyType k, ValueType v)
   {
      key = k;
      value = v;
      prev = null;
      next = null;
   }

   public String toString()
   {
      return( "(" + key + "," + value + ")" );
   }
}