Question

我正在尝试学习装饰模式，但我遇到了问题。

首先我有一个界面

public interface MyCar {
    public String getMessage(int speed);
    public int getPrice();
}

我像这样实现了这个类;

public class Car implements MyCar{
    protected int price;
    protected boolean feature1;
    protected boolean feature2;

    public Car(){
        this.price = 0;
        this.feature1 = false;
        this.feature2 = false;
    }
    publicCar(int price){
        this.price = price;
        this.feature1 = false;
        this.feature2 = false;
    }

    int getPrice(){
        return price + (feature1 ? 1000 : 0) + (feature2 ? 2000 : 0);
    }
}

之后我从这个班级派生了两辆汽车，如

public class Car1 extends Car{
    private static int price = 20000;

    public Car1() {
        super(price);
    }
}

Car2类完全相同，但价格为30000。

在此之后我创建了一个汽车装饰器类;

public abstract class CarDecorator extends Car {
    protected Car decoratedCar;

    public CarDecorator(){
        decoratedCar = new Car();
    }

    public CarDecorator(Car decoratedCar) {
        this.decoratedCar = decoratedCar;
    }

    public int getPrice(){
        return this.decoratedCar.getPrice();
    }
}

最后我创建了2个源自CarDecorator的decorater类：

public class F1Decorator extends CarDecorator{

    public F1Decorator(Car car) {
        super(car);
        decoratedCar.feature1 = true;
    }
}

public class F2Decorator extends CarDecorator{

    public F2Decorator(Car car) {
        super(car);
        decoratedCar.feature2 = true;
    }
}

public class Test {

    public static void main(String[] args){

        Car car1 = new Car1();
        System.out.println("Price: " + car1.getPrice());

        car1 = new F1Decorator(car1);
        System.out.println("Price: " + car1.getPrice());

        car1 = new F2Decorator(car1);
        System.out.println("Price: " + car1.getPrice());
    }
}

输出

Price: 20000
Price: 21000
Price: 21000

为什么feature2对car1没有任何影响。我的设计出了什么问题。如果你能提供帮助，我想我会非常了解装饰模式。

Answer 1

当您使用car1装饰F1Decorator时，会返回F1Decoorator，即Car。构造函数在原始feature1上设置car1。这辆新装修的汽车被分配回car1。

但是，当您使用car1再次装饰F2Decorator时，您正在装饰F1Decorator，而不是原始Car。您正在设置F1Decorator的{{1}}，而不是原始feature2的{{1}}。因此，原始Car上的feature2仍为feature2，价格仍为Car。

介绍并调用false上的方法以及将通过功能设置传递给21000的装饰器类。

在Car：

Car

在Car：

public void setFeature1(boolean feat1)
{
   this.feature1 = feat1;
}

public void setFeature2(boolean feat2)
{
   this.feature2 = feat2;
}

在CarDecorator：

public void setFeature1(boolean feat1)
{
   this.decoratedCar.setFeature1(feat1);
}

public void setFeature2(boolean feat2)
{
   this.decoratedCar.setFeature2(feat2);
}

在F1Decorator：

public F1Decorator(Car car) {
    super(car);
    // Replace the assignment with this line.
    decoratedCar.setFeature1(true);
}

通过这些更改，输出现在为：

F2Decorator

装饰模式的麻烦

1 个答案: