CSC301: Put: Recursive [15/30]

    public void putLeft (int key) {
        if (root==null) {
            root = new Node (key);
        } else {
            putLeft (root, key);
        }
    }
    private static void putLeft (Node x, int key) {
        if (x.left == null)
            x.left = new Node (key);
        else {
            putLeft (x.left, key);
        }
    }

Make it recursive.