CSC301: Printing: Print infix with a loop [27/30]

    public void printIn () {
        Stack<Node> s = new Stack<> ();
        Node x = root;
        while (x != null || !s.isEmpty ()) {
            if (x != null) {
                s.push (x);
                x = x.left;
            } else {
                x = s.pop ();
                StdOut.print (x.key + " ");
                x = x.right;
            }
        }
        StdOut.println ();
    }

Print infix with a loop (from here)

Yeesh.