class Engine {

  def start(): Unit = {

    println("Engine started")

  }

}

​

class Car {

  val engine = new Engine()

​

  def startCar(): Unit = {

    engine.start()

    println("Car started")

  }

}

​

object Main {

  def main(args: Array[String]): Unit = {

    val myCar = new Car()

    myCar.startCar()

  }

}