ActorSystem system = ActorSystem.create("calculator-system");
ActorRef calculatorService =
system.actorOf(Props.create(ArithmeticService.class), "arithmetic-service");
// (3 + 5) / (2 * (1 + 1))
Expression task = new Divide(
new Add(new Const(3), new Const(5)),
new Multiply(
new Const(2),
new Add(new Const(1), new Const(1))
)