// To simplify the implementation, I'm making the attributes "protected".
// This means they will be accessible to other classes in the same
// directory, but not accessible from beyond the directory containing
// this file.  This will save us having lots of cumbersome get/set methods.
// To make the implementation general, we say that the node contains some
// "Item" object, which presumably extends the Object class to provide
// an implementation of equals() and toString().
public class Node
{
  protected Node prev;
  protected Node next;
  protected Item data;    

  public Node(Item value)
  {
    prev = null;
    next = null;
    data = value;
  }
}