public abstract class Vehicle {
    private Engine engine;
    private Tire tires;

    public Engine getEngine() {
        return engine;
    }

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

    public Tire getTires() {
        return tires;
    }

    public void setTires(Tire tires) {
        this.tires = tires;
    }

    public MotorVehicle() {
        super();
    }

    public Vehicle(Engine engine, Tire tires) {
        this.engine = engine;
        this.tires = tires;
    }
}

public class Car extends Vehicle {
    private Engine engine;
    private Tire tires;
    private ExhaustSystem system;

    public Car() {
        super();
    }

    public Car(Engine engine, Tire tires) {
        super(engine, tires);
    }
}

public interface Engine {
    String getType();
    ExhaustSystem getExhaustSystem();
}

public class DieselEngine implements Engine {
    private String type;
    private DieselExhaustSystem system;

    public DieselEngine(String type, DieselExhaustSystem system) {
        this.type = type;
        this.system = system;
    }

    @Override
    public String getType() {
        return type;
    }
    @Override
    public ExhaustSystem getExhaustSystem() {
        return system;
    }
}

public interface ExhaustSystem {
    double getGasExits();
}

public class DieselExhaustSystem implements ExhaustSystem {

    /**
     *
     * @return CO2 emission units.
     */
    @Override
    public double getGasExits() {
        return 3;
    }
}