public void addItem(LineItem anItem){
		String iSBN = anItem.getTheBook().getCode();
		for (int i = 0; i < items.size(); i++) {
			LineItem currentItem = items.get(i);
			if (currentItem.getTheBook().getCode().equals(iSBN)) {
				currentItem.setQuantity(anItem.getQuantity());;
				return;
			}
		}
		items.add(anItem);
	}