public boolean addInventory(int productId, int inventoryChange) {
		try {
			Connection conn = openConnection();

			Statement stat = conn.createStatement();
			ResultSet rs = stat.executeQuery("select inventory from "
					+ DB_PRODUCT_TABLE + " where rowid = " + productId + ";");
			inventoryChange += rs.getInt("inventory");
			if(inventoryChange < 0)
			{
				rs.close();
				conn.close();
				return false;
			}

			PreparedStatement prep = conn.prepareStatement("update "
					+ DB_PRODUCT_TABLE + " set inventory = ? where rowid = ?");
			prep.setInt(1, inventoryChange);
			prep.setInt(2, productId);
			prep.execute();
			rs.close();
			conn.close();
			return true;
		} catch (Exception e) {
			e.printStackTrace();
		}
		return false;
	}