如何使用Java实现对象能力的动态扩展_利用装饰模式增强行为

// 抽象组件：饮料
interface Beverage {
    String getDescription();
    double getCost();
}

// 具体组件：基础咖啡
class Coffee implements Beverage {
    public String getDescri
ption() {
        return "咖啡";
    }

    public double getCost() {
        return 10.0;
    }
}

// 装饰器基类
abstract class CondimentDecorator implements Beverage {
    protected Beverage beverage;

    public CondimentDecorator(Beverage beverage) {
        this.beverage = beverage;
    }
}

// 具体装饰器：加糖
class Sugar extends CondimentDecorator {
    public Sugar(Beverage beverage) {
        super(beverage);
    }

    public String getDescription() {
        return beverage.getDescription() + " + 糖";
    }

    public double getCost() {
        return beverage.getCost() + 1.0;
    }
}

// 具体装饰器：加牛奶
class Milk extends CondimentDecorator {
    public Milk(Beverage beverage) {
        super(beverage);
    }

    public String getDescription() {
        return beverage.getDescription() + " + 牛奶";
    }

    public double getCost() {
        return beverage.getCost() + 2.5;
    }
}

// 使用示例
public class Main {
    public static void main(String[] args) {
        Beverage order = new Coffee();           // 基础咖啡
        order = new Milk(order);                 // 加牛奶
        order = new Sugar(order);                // 再加糖

        System.out.println("描述: " + order.getDescription());
        System.out.println("总价: " + order.getCost()); 
        // 输出：描述: 咖啡 + 牛奶 + 糖
        // 输出：总价: 13.5
    }
}