interface BinNode { // Binary tree node ADT
  // Get and set the element value
  public Object value();
  public void setValue(Object v);

  // return the children
  public BinNode left();
  public BinNode right();

  // return TRUE if a leaf node, FALSE otherwise
  public boolean isLeaf();
}

interface BinNode<E> { // Binary tree node ADT
  // Get and set the element value
  public E value();
  public void setValue(E v);

  // return the children
  public BinNode<E> left();
  public BinNode<E> right();

  // return TRUE if a leaf node, FALSE otherwise
  public boolean isLeaf();
}

static void preorder(BinNode rt) {
  if (rt == null) return; // Empty subtree - do nothing
  visit(rt);              // Process root node
  preorder(rt.left());    // Process all nodes in left
  preorder(rt.right());   // Process all nodes in right
}

static <E> void preorder(BinNode<E> rt) {
  if (rt == null) { return; } // Empty subtree - do nothing
  visit(rt);              // Process root node
  preorder(rt.left());    // Process all nodes in left
  preorder(rt.right());   // Process all nodes in right
}

// This is a bad idea
static void preorder2(BinNode rt) {
  visit(rt);
  if (rt.left() != null) preorder2(rt.left());
  if (rt.right() != null) preorder2(rt.right());
}

// This is a bad idea
static <E> void preorder2(BinNode<E> rt) {
  visit(rt);
  if (rt.left() != null) { preorder2(rt.left()); }
  if (rt.right() != null) { preorder2(rt.right()); }
}

static int count(BinNode rt) {
  if (rt == null) return 0;  // Nothing to count
  return 1 + count(rt.left()) + count(rt.right());
}

static <E> int count(BinNode<E> rt) {
  if (rt == null) { return 0; }  // Nothing to count
  return 1 + count(rt.left()) + count(rt.right());
}