How to create an object from a class that delegates methods?

Question

I'm following the below UML to create the classes that call delegate methods from an engine class, but when I tired to create an object of the Ferrari class and pass it the type of engine, ie a CombustionEngine.

I get the error CombustionEngine cannot be resolved to a variable.

I gather from this that the enzo object can't see the CombustionEngine class that is extended from the Engine interface.

Can anyone see where I have gone wrong with the implementation of the hierarchy?

The CombustionEngine class extended from Engine interface:

public class CombustionEngine implements Engine {

    //instance variables
    private int speed;



    public CombustionEngine(int speed) {
        super();
        this.speed = speed;
    }


    public CombustionEngine() {
        super();
        // TODO Auto-generated constructor stub
    }


    public void setSpeed(int speed) {
        this.speed = speed;
    }



    @Override
    public void stop() {
        // TODO Auto-generated method stub
        System.out.println("Combustion engine Stopped:"); 
    }

    @Override
    public void start() {
        // TODO Auto-generated method stub
        System.out.println("Combustion engine Startedd:"); 

    }

    @Override
    public void throttle(int power) {
        // TODO Auto-generated method stub
        speed += power;
    }

    @Override
    public int getSpeed() {
        // TODO Auto-generated method stub
        return speed;
    }   


}

The Engine interface:

public interface Engine {

    void stop();
    void start();
    void throttle(int power);
    int getSpeed();

}

PowerVehicle class:

public class PoweredVehicle  {


    Engine engine;

    public PoweredVehicle(Engine engine) {
        super();
        this.engine = engine;
    }

    public Engine getEngine() {
        return engine;
    }


    public void  Drive(){


        System.out.println("Generic Driving");

    }

    public void setEngine(Engine engine) {
        this.engine = engine;
    }

    public void stop() {
        engine.stop();
    }

    public void start() {
        engine.start();
    }

    public void throttle(int power) {
        engine.throttle(power);
    }

    public int getSpeed() {
        return engine.getSpeed();
    }




}

The Ferrari class:

public class Ferrari extends PoweredVehicle {

    public Ferrari(Engine engine) {
        super(engine);
        // TODO Auto-generated constructor stub
    }

    Ferrari f = new Ferrari(engine);

    @Override
    public void Drive() {
        // TODO Auto-generated method stub
        super.Drive();
        System.out.println("Ferrari driving...");


    }   

}

Finally in the Runner class I try to create an instance of Ferrari

public class Runner {

    public Runner() {
        // TODO Auto-generated constructor stub
    }


    public static void main(String[] args) {

        Ferrari enzo = new Ferrari(CombustionEngine);



    }

}

Answer 1

Why are you creating an instance of Ferrari inside the Ferrari class?

public class Ferrari extends PoweredVehicle
{   
    public Ferrari(Engine engine) {
        super(engine);
    }

    Ferrari f = new Ferrari(engine); // Why would you do this here?

    @Override
    public void Drive() {
        super.Drive();
        System.out.println("Ferrari driving...");
    } 
}

And you have to pass in an instance of CombustionEngine, when creating a Ferrari object

public static void main(String[] args)
{
    int someSpeed = 99;
    Ferrari enzo = new Ferrari(new CombustionEngine(someSpeed));
}

Here, you are implementing an interface, so there should not be a need for super()

public class CombustionEngine implements Engine
{
    //instance variables
    private int speed;

    public CombustionEngine(int speed)
    {
        //super();
        this.speed = speed;
    }
    ....
}