常用设计模式——装饰模式

/**
 * 饮料
 * @author huangy on 2019-05-19
 */
public abstract class Beverage {

    String description = "Unknown Beverage";

    public String getDescription() {
        return description;
    }

    public abstract double cost();
}

/**
 * 调料（装饰者抽象类）
 * @author huangy on 2019-05-19
 */
public abstract class CondimentDecorator extends Beverage {

    public abstract String getDescription();
    
}

/**
 * 浓缩咖啡
 * @author huangy on 2019-05-19
 */
public class Espresso extends Beverage {

    public Espresso() {
        description = "Espresso";
    }

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

/**
 * @author huangy on 2019-05-19
 */
public class Mocha extends CondimentDecorator {

    Beverage beverage;

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

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

    @Override
    public double cost() {
        return 0.20 + beverage.cost();
    }
}

public class StarbuzzCoffee {

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

        Mocha mocha = new Mocha(beverage);

        System.out.println(mocha.getDescription());

        System.out.println(mocha.cost());
    }

}