Illegal Operation On Empty Result Set

ane masih newbie untuk netbeans agan semua. ni kodingan saya gan. studi kasus metode least cost. ketika mau di hitunt untuk tombol hitungnya eror gan.
int i = 0;
            while(rs2.next()){
                int j = 0;

                while (rs.next()){
                   // System.out.println("select total_biaya from biaya where id_gudang="+rs.getString(1)+" and id_toko='"+rs2.getString(2)+"'");
                    ResultSet rs3 = cn.createStatement().executeQuery("select total_biaya from biaya where id_sumber='"+rs.getString(1)+"' and id_tangki='"+rs2.getString(2)+"'");
                    rs3.next();
                    biaya[j][i] = Double.parseDouble(rs3.getString(1));
                    biayaoptimal[j][i] = Double.parseDouble(rs3.getString(1));

                    j++;

                }
                rs.beforeFirst();
                demand[i] = Integer.parseInt(rs2.getString(3));

                i++;
            }