讀書筆記3：Head First設計模式——裝飾者模式

  設計原則：

類應該對擴充開放，對修改關閉。

   裝飾者模式：

動態地將責任附加到對象上。若要擴充功能，裝飾者提供了比繼承更有彈性的代替方案。

裝飾者和被裝飾者必須是一樣的類型，也就是有共同的超類。

public abstract class Beverage {String description = "Unknown Beverage";int size;public String getDescription() {return description;}public int getSize() {return size;}public abstract double cost();}

public abstract class CondimentDecorator extends Beverage {public abstract String getDescription();}

public class HouseBlend extends Beverage {public HouseBlend() {description = "House Blend Coffee";}@Overridepublic double cost() {return 0.89;}}

public class DarkRoast extends Beverage {public DarkRoast() {description = "Dark Roast Coffee";}@Overridepublic double cost() {return .99;}}

public class Espresso extends Beverage {public Espresso() {description = "Espresso";}@Overridepublic double cost() {return 1.99;}}

public class Mocha extends CondimentDecorator {Beverage beverage;public Mocha(Beverage beverage) {this.beverage = beverage;}@Overridepublic String getDescription() {return beverage.getDescription() + ", Mocha";}@Overridepublic double cost() {return 0.20 + beverage.cost();}}

public class Soy extends CondimentDecorator {Beverage beverage;public Soy(Beverage beverage) {this.beverage = beverage;}public String getDescription() {return beverage.getDescription() + ", Soy";}public double cost() {return .15 + beverage.cost();}}

public class Whip extends CondimentDecorator {Beverage beverage; public Whip(Beverage beverage) {this.beverage = beverage;} public String getDescription() {return beverage.getDescription() + ", Whip";} public double cost() {return .10 + beverage.cost();}}

public class StarbuzzCoffee {public static void main(String[] args) {Beverage beverage = new Espresso();System.out.println(beverage.getDescription()+ " $" + beverage.cost());Beverage beverage2 = new DarkRoast();beverage2 = new Mocha(beverage2);beverage2 = new Mocha(beverage2);beverage2 = new Whip(beverage2);System.out.println(beverage2.getDescription()+ " $" + beverage2.cost());Beverage beverage3 = new HouseBlend();beverage3 = new Soy(beverage3);beverage3 = new Mocha(beverage3);beverage3 = new Whip(beverage3);System.out.println(beverage3.getDescription()+ " $" + beverage3.cost());}}