public void addItem(final StockItem stockItem) {
		try {
			StockItem item = getItemById(stockItem.getId());
			item.setQuantity(item.getQuantity() + stockItem.getQuantity());
			log.debug("Found existing item " + stockItem.getName()
					+ " increased quantity by " + stockItem.getQuantity());
		}
		catch (NoSuchElementException e) {
			rows.add(stockItem);
			log.debug("Added " + stockItem.getName()
					+ " quantity of " + stockItem.getQuantity());
		}
		fireTableDataChanged();
	}