Java对象组合实现装饰器动态增强

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

class SimpleCoffee implements Coffee {
    public String getDescription() { return "Simple coffee"; }
    public double getCost() { return 2.0; }
}

abstract class CoffeeDecorator implements Coffee {
    protected final Coffee coffee;

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

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

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

class MilkDecorator extends CoffeeDecorator {
    MilkDecorator(Coffee coffee) {
        super(coffee);
    }

    @Override
    public String getDescription() {
        return coffee.getDescription() + ", milk";
    }

    @Override
    public double getCost() {
        return coffee.getCost() + 0.5;
    }
}

class CaramelDecorator extends CoffeeDecorator {
    CaramelDecorator(Coffee coffee) {
        super(coffee);
    }

    @Override
    public String getDescription() {
        return coffee.getDescription() + ", caramel";
    }

    @Override
    public double getCost() {
        return coffee.getCost() + 0.7;
    }
}

Coffee order = new SimpleCoffee();
order = new MilkDecorator(order);
order = new CaramelDecorator(order);
System.out.println(order.getDescription()); // Simple coffee, milk, caramel
System.out.println(order.getCost());          // 3.2