global java.util.List list
rule R when
  $t : CarType(id == \"roadster\")
  accumulate(
    $c : Car(type == $t);
    $total : count($c)
  )\
then
  list.addAll(kcontext.getMatch().getObjects());
end

        CarType roadsterType = new CarType("roadster");
        ksession.insert(roadsterType);
        Car bmwZ4 = new Car("BMW Z4", roadsterType);
        ksession.insert(bmwZ4);
        Car lotusElise = new Car("Lotus Elise", roadsterType);
        ksession.insert(lotusElise);
        Car mazdaMx5 = new Car("Mazda MX-5", roadsterType);
        ksession.insert(mazdaMx5);