@SuppressWarnings("unchecked")
class Stacks {
    public static <E> Stack<E> reverse(Stack<E> in) {
	Stack out = new ArrayStack();
        while (!in.empty()) {
	    Object elt = in.pop();
	    out.push(elt);  // unchecked call
	}
	return out;  // unchecked conversion
    }
}