裝飾者模式: 動態的將新功能附加到對象上, 在對象功能擴展方面,它比繼承更有彈性,裝飾者模式也體現了開閉原則(OCP).

java的IO結構,FileInputStream就是一個裝飾者

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public abstract class Drink {public String desc; // 描述private float price = 0.0f;public String getDesc() {return desc;}public void setDesc(String desc) {this.desc = desc;}public float getPrice() {return price;}public void setPrice(float price) {this.price = price;}// 計算費用, 由子類實現public abstract float cost(); }public class Coffee extends Drink{@Overridepublic float cost() {return getPrice();}}public class Espresso extends Coffee{public Espresso(){setDesc(" 意大利咖啡 ");setPrice(6.0f);} }public class LongBlack extends Coffee{public LongBlack(){setDesc(" LongBlack ");setPrice(5.0f);} }public class ShortBlack extends Coffee{public ShortBlack(){setDesc(" ShortBlack ");setPrice(4.0f);} }裝飾者 public class Decorator extends Drink{private Drink obj;public Decorator(Drink obj){this.obj = obj;}@Overridepublic float cost() {return getPrice() + obj.cost();}@Overridepublic String getDesc() {return desc +" "+getPrice() +" && "+obj.getDesc();} }public class Chocolate extends Decorator{public Chocolate(Drink obj) {super(obj);setDesc(" 巧克力 ");setPrice(3.0f);} }public class Milk extends Decorator{public Milk(Drink obj) {super(obj);setDesc(" 牛奶 ");setPrice(2.0f);} }public class Soy extends Decorator{public Soy(Drink obj) {super(obj);setDesc(" 豆漿 ");setPrice(1.5f);} }public class Client {public static void main(String[] args){Drink order = new LongBlack();order = new Milk(order);System.out.println("加一分牛奶 "+order.getDesc());order = new Chocolate(order);System.out.println("加一分牛奶 加一份巧克力 "+order.getDesc());order = new Chocolate(order);System.out.println("加一分牛奶 加兩份巧克力 "+order.getDesc());System.out.println(order.cost());} }

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