Java中装饰器模式的作用 解析装饰器模式动态扩展功能的特点

interface Coffee {
    String getDescription();
    double cost();
}

class SimpleCoffee implements Coffee {
    @Override
    public String getDescription() {
        return "Simple Coffee";
    }

    @Override
    public double cost() {
        return 1.0;
    }
}

abstract class CoffeeDecorator implements Coffee {
    protected Coffee coffee;

    public CoffeeDecorator(Coffee coffee) {
        this.coffee = coffee;
    }

    @Override
    public String getDescription() {
        return coffee.getDescription();
    }

    @Override
    public double cost() {
        return coffee.cost();
    }
}

class MilkCoffee extends CoffeeDecorator {
    public MilkCoffee(Coffee coffee) {
        super(coffee);
    }

    @Override
    public String getDescription() {
        return super.getDescription() + ", with Milk";
    }

    @Override
    public double cost() {
        return super.cost() + 0.5;
    }
}

class SugarCoffee extends CoffeeDecorator {
    public SugarCoffee(Coffee coffee) {
        super(coffee);
    }

    @Override
    public String getDescription() {
        return super.getDescription() + ", with Sugar";
    }

    @Override
    public double cost() {
        return super.cost() + 0.2;
    }
}

public class Main {
    public static void main(String[] args) {
        Coffee coffee = new SimpleCoffee();
        System.out.println("Cost: " + coffee.cost() + ", Description: " + coffee.getDescription());

        Coffee milkCoffee = new MilkCoffee(coffee);
        System.out.println("Cost: " + milkCoffee.cost() + ", Description: " + milkCoffee.getDescription());

        Coffee sugarMilkCoffee = new SugarCoffee(milkCoffee);
        System.out.println("Cost: " + sugarMilkCoffee.cost() + ", Description: " + sugarMilkCoffee.getDescription());
    }
}