如何从委派方法的类创建对象？

Question

我按照下面的UML来创建从引擎类调用委托方法的类，但是当我厌倦了创建法拉利类的对象并将其传递给引擎类型时，即{{1 }}。

我收到错误CombustionEngine。

我从中收集到CombustionEngine cannot be resolved to a variable对象无法看到从enzo界面扩展的CombustionEngine类。

任何人都可以看到我在层次结构的实现方面出了什么问题吗？

从Engine扩展的CombustionEngine课程：

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; } } 界面：

Engine

public interface Engine { void stop(); void start(); void throttle(int power); int getSpeed(); } 上课：

PowerVehicle

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(); } } 类：

Ferrari

最后在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..."); } } 课程中，我尝试创建Runner

的实例

Ferrari

Answer 1

 Ferrari enzo = new Ferrari(CombustionEngine);

您的Ferrari课程需要 Engine 类型的实例。 CombusionEngine本身毫无意义。它是一个在内存中没有任何内容的名称。您需要先创建CombustionEngine，然后将其传入。有点像......

 CombustionEngine engine = new CombustionEngine(100); // Or whatever your speed is.

 Ferrari enzo = new Ferrari(engine);

显然可以变成匿名对象..

 Ferrari enzo = new Ferrari(new CombustionEngine(100));

Answer 2

为什么要在Ferrari类中创建Ferrari的实例？

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...");
    } 
}

在创建Ferrari对象

时，您必须传入CombustionEngine的实例

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

在这里，您正在实现一个接口，因此不需要super()

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

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