count_both_child

private int count_who_have_both_children(Node node){
    int x, y;
    if (node != null){
        x = count_who_have_both_children(node.left);
        y = count_who_have_both_children(node.right);
        if (node.left != null && node.right != null){
            return x + y + 1;
        }else {
            return x + y;
        }
    }
    return 0;
}