public class Node
{
   public Entry[] e;
   public Node[] child;
   public Node   parent;

   /* =====================================================
      Node(): a 2-4 node contains 4 subtress (and 3 keys)
      ===================================================== */
   public Node()
   {
      int i;

      e = new Entry[3];
      child = new Node[4];

      for ( i = 0; i < 3 ; i++ )
      {
         e[i] = null;
      }

      for ( i = 0; i < 4 ; i++ )
        child[i] = null;

      parent = null;
   }

   public String toString()
   {
     return ( "("
             + ((e[0]==null)?"(-)":e[0].key) + ","
             + ((e[1]==null)?"(-)":e[1].key) + ","
             + ((e[2]==null)?"(-)":e[2].key) + ")" );
   }
}