Assume a private Node class is used for an AVL tree class:

public class AVL<E extends Comparable<E>>
{
  // AVL members and methods
  ...

     // inner class
     private static Node 
     {
       public E data;
       public Node left;
       public Node right;
       public int height; // optional

       public  Node() {}
       public Node(E x) {
         data = x;
         height = 0; // optional
       }
     }
}