public class AnyWildCardDemo {
    public static void main(String [] args)
    {
        GenericStack<Integer> intStack = new GenericStack<>();
        intStack.push(1);
        intStack.push(2);
        intStack.push(3);
        print(intStack);
    }
    //<?> is equivalent with <? extends Object>

    public static void print(GenericStack<?> stack)
    {
        while(!stack.isEmpty())
        {
            System.out.print(stack.pop() + " ");
        }
    }
}