To find the successor of x in a BST

The last left turn is the successor(x):

public E successor(E x){
return succAux(root, x, null);
}

public E succAux(Node root, E x, E best){
if(root==null)
return best;
int c=x.compartTo(root);
if(c>0)
return succAux(root.right, X, best);
else
return succAux(root.l, X, root.v);
}