设计模式之装饰模式

Beverage.java

public abstract class Beverage {

    String description = "Unknown Berverage";

    public String getDescription(){
        return description;
    }

    public abstract double cost();
}

CondimentDecorator.java

public abstract class CondimentDecorator extends Beverage {

    public abstract String getDescription();

}

Espresso.java

public class Espresso extends Beverage {

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

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

HouseBlend.java

public class HouseBlend extends Beverage {

    public HouseBlend() {
        description = "House Blend Coffee";
    }

    @Override
    public double cost() {
        return .89;
    }
}

Mocha.java

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 .20 + beverage.cost();
    }
}

Starbuzzcoffee.java

public class Starbuzzcoffee {

    public static void main(String[] args) {
        Beverage beverage = new Espresso();
        System.out.println(beverage.getDescription() + "$" + beverage.cost());

        Beverage beverage2 = new Espresso();
        beverage2 = new Mocha(beverage2);
        beverage2 = new Mocha(beverage2);
        System.out.println(beverage2.getDescription() + "$" + beverage2.cost());

        Beverage beverage3 = new HouseBlend();
        beverage3 = new Mocha(beverage3);
        System.out.println(beverage3.getDescription() + "$" + beverage3.cost());       
    }
}