public class Driver
{
    public static void main (String [] args)
    {
        Inventory chinook = new Inventory ();
        chinook.add(10);
        System.out.println(chinook.showStockLevel());
	   chinook.add(10);
        System.out.println(chinook.showStockLevel());
        chinook.add(100);
        System.out.println(chinook.showStockLevel());
        chinook.remove(21);
        System.out.println(chinook.showStockLevel());
        // JT: The statement below won't work and for good reason! 
        // chinook.stockLevel = -999;
    }
}