代码实例

/**
 * 基础组件
 */
abstract class Beverage {

    private String description = "Unknown Beverage";

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public abstract double cost();
}

/**
 * 装饰器基类
 */
abstract class Decorator extends Beverage {

    @Override
    public abstract String getDescription();
}

/**
 * 被装饰的类
 */
class Espresso extends Beverage {

    public Espresso() {
        setDescription("Espresso");
    }

    @Override
    public double cost() {
        return 1.99;
    }
}

/**
 * 装饰器
 */
class Mocha extends Decorator {

    private Beverage beverage;

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

    @Override
    public double cost() {
        return beverage.cost() + 0.29;
    }

    @Override
    public String getDescription() {
        return beverage.getDescription() + ", Mocha";
    }
}

class CoffeeTest {
    public static void main(String[] args) {
        Beverage beverage = new Espresso();
        beverage = new Mocha(beverage);

        System.out.println(beverage.getDescription() + " " + beverage.cost());
    }
}