什么是装饰器模式? 【先吃三颗栗子:】 1.PC=主机+显示器+键盘+鼠标+鼠标垫 主机是核心,而其他的组成部分都是装饰。 2.手抓饼=饼+鸡蛋+培根+黄瓜 饼是核心,鸡蛋,培根是可选的,可以理解为装饰。 3.咖啡=咖啡+牛奶+冰+方糖 咖啡是核心,牛奶等可选。 比喻虽然形象生动,但是与实际或多或少会产生偏差。 抽象的解释:装饰器模式的目的——核心部分和装饰部分可以自由组合。 装饰器模式的功能 对于软件开发来说,聚焦于软件的灵活性和可扩展性。 装饰器模式要求: 装饰可选 装饰可扩展 核心部分可扩展 手抓饼中的装饰器模式 实现饼加各种配料的价格计算。 思路: 1.定义抽象类手抓饼,其中包含获取种类的抽象方法和获取价格的抽象方法。 2.然后定义两个分别为大份手抓饼和中份手抓饼来继承这个抽象类,重写两个方法定义种类和价格。 3.定义具体的配料类继承手抓饼抽象类,先定义构造器传入已经创建的手抓饼种类,然后重写种类和价格方法。 在网上看的一些博客,是创建出一个抽象的配料类来继承抽象产品类,然后用具体的配料类来实现抽象配料类,实现装饰。 可是如果直接将抽象产品类的方法全部定义抽象方法,配料类直接继承重写,实现装饰,功能上也是可以实现的,如下所示,Bacon类直接继承HandPancake,然后重写getName和getCost方法,实现装饰。似乎也没有问题: 但是设计模式毕竟是一种经验总结,如果有已经看出端倪的小伙伴们在下方留言交流一下吧! 直接继承HandPancake: abstract class HandPancake { public abstract String getName(); public abstract int getCost(); } class HandPancake_Big extends HandPancake { @Override public String getName() { return "大份手抓饼"; } @Override public int getCost() { return 10; } } class HandPancake_Mid extends HandPancake { @Override public String getName() { return "中份手抓饼"; } @Override public int getCost() { return 8; } } class Bacon extends HandPancake { private HandPancake handPancake; Bacon(HandPancake handPancake) { this.handPancake=handPancake; } @Override public String getName() { return handPancake.getName()+"加培根"; } @Override public int getCost() { return handPancake.getCost()+1; } } class Cucumber extends HandPancake { private HandPancake handPancake; Cucumber(HandPancake handPancake) { this.handPancake=handPancake; } @Override public String getName() { return handPancake.getName()+"加黄瓜"; } @Override public int getCost() { return handPancake.getCost()+2; } } class Ham extends HandPancake { private HandPancake handPancake; Ham(HandPancake handPancake) { this.handPancake=handPancake; } @Override public String getName() { return handPancake.getName()+"加火腿"; } @Override public int getCost() { return handPancake.getCost()+1; } } public class APPlication { public static void main(String[] args) { HandPancake handPancake_big = new HandPancake_Big(); System.out.println("啥也不加"+handPancake_big.getName()+":"+handPancake_big.getCost()); handPancake_big = new Ham(handPancake_big); System.out.println(handPancake_big.getName()+":"+handPancake_big.getCost()); handPancake_big = new Cucumber(handPancake_big); System.out.println(handPancake_big.getName()+":"+handPancake_big.getCost()); handPancake_big = new Bacon(handPancake_big); System.out.println(handPancake_big.getName()+":"+handPancake_big.getCost()); System.out.println("=============================="); HandPancake handPancake_mid = new HandPancake_Mid(); System.out.println("啥也不加"+handPancake_mid.getName()+":"+handPancake_mid.getCost()); handPancake_mid = new Ham(handPancake_mid); System.out.println(handPancake_mid.getName()+":"+handPancake_mid.getCost()); handPancake_mid = new Cucumber(handPancake_mid); System.out.println(handPancake_mid.getName()+":"+handPancake_mid.getCost()); handPancake_mid = new Bacon(handPancake_mid); System.out.println(handPancake_mid.getName()+":"+handPancake_mid.getCost()); } } 官方做法: abstract class HandPancake { String name; //1 public String getName() { return name; } public abstract int getCost(); } class HandPancake_Big extends HandPancake { HandPancake_Big() //2.通过构造器赋值 { name="大份手抓饼"; } @Override public int getCost() { return 10; } } class HandPancake_Mid extends HandPancake { HandPancake_Mid() //2.通过构造器赋值 { name="中份手抓饼"; } @Override public int getCost() { return 8; } } abstract class Condiments extends HandPancake //3.定义抽象接口 { public abstract String getName(); } class Bacon extends Condiments //4.继承抽象接口 { private HandPancake handPancake; Bacon(HandPancake handPancake) { this.handPancake=handPancake; } @Override public String getName() { return handPancake.getName()+"加培根"; } @Override public int getCost() { return handPancake.getCost()+1; } } class Cucumber extends Condiments { private HandPancake handPancake; Cucumber(HandPancake handPancake) { this.handPancake=handPancake; } @Override public String getName() { return handPancake.getName()+"加黄瓜"; } @Override public int getCost() { return handPancake.getCost()+2; } } class Ham extends Condiments { private HandPancake handPancake; Ham(HandPancake handPancake) { this.handPancake=handPancake; } @Override public String getName() { return handPancake.getName()+"加火腿"; } @Override public int getCost() { return handPancake.getCost()+1; } } public class APPlication { public static void main(String[] args) { HandPancake handPancake_big = new HandPancake_Big(); System.out.println("啥也不加"+handPancake_big.getName()+":"+handPancake_big.getCost()); handPancake_big = new Ham(handPancake_big); System.out.println(handPancake_big.getName()+":"+handPancake_big.getCost()); handPancake_big = new Cucumber(handPancake_big); System.out.println(handPancake_big.getName()+":"+handPancake_big.getCost()); handPancake_big = new Bacon(handPancake_big); System.out.println(handPancake_big.getName()+":"+handPancake_big.getCost()); System.out.println("=============================="); HandPancake handPancake_mid = new HandPancake_Mid(); System.out.println("啥也不加"+handPancake_mid.getName()+":"+handPancake_mid.getCost()); handPancake_mid = new Ham(handPancake_mid); System.out.println(handPancake_mid.getName()+":"+handPancake_mid.getCost()); handPancake_mid = new Cucumber(handPancake_mid); System.out.println(handPancake_mid.getName()+":"+handPancake_mid.getCost()); handPancake_mid = new Bacon(handPancake_mid); System.out.println(handPancake_mid.getName()+":"+handPancake_mid.getCost()); } } 手抓饼的扩展性 创建手抓饼的种类 创建配料种类 官方的扩展:创建一个小份手抓饼继承Hanpancake,然后创建配料继承Condiments。 贴一下直接继承HandPancake的情况: class HandPancake_Smalll extends HandPancake class Egg extends HandPancake abstract class HandPancake { public abstract String getName(); public abstract int getCost(); } class HandPancake_Big extends HandPancake { @Override public String getName() { return "大份手抓饼"; } @Override public int getCost() { return 10; } } class HandPancake_Mid extends HandPancake { @Override public String getName() { return "中份手抓饼"; } @Override public int getCost() { return 8; } } class Bacon extends HandPancake { private HandPancake handPancake; Bacon(HandPancake handPancake) { this.handPancake=handPancake; } @Override public String getName() { return handPancake.getName()+"加培根"; } @Override public int getCost() { return handPancake.getCost()+1; } } class Cucumber extends HandPancake { private HandPancake handPancake; Cucumber(HandPancake handPancake) { this.handPancake=handPancake; } @Override public String getName() { return handPancake.getName()+"加黄瓜"; } @Override public int getCost() { return handPancake.getCost()+2; } } class Ham extends HandPancake { private HandPancake handPancake; Ham(HandPancake handPancake) { this.handPancake=handPancake; } @Override public String getName() { return handPancake.getName()+"加火腿"; } @Override public int getCost() { return handPancake.getCost()+1; } } //======================== class HandPancake_Smalll extends HandPancake { @Override public String getName() { return "小份手抓饼"; } @Override public int getCost() { return 5; } } class Egg extends HandPancake { private HandPancake handPancake; Egg(HandPancake handPancake) { this.handPancake=handPancake; } @Override public String getName() { return handPancake.getName()+"加鸡蛋"; } @Override public int getCost() { return handPancake.getCost()+1; } } public class APPlication { public static void main(String[] args) { HandPancake handPancake_big = new HandPancake_Big(); System.out.println("啥也不加"+handPancake_big.getName()+":"+handPancake_big.getCost()); handPancake_big = new Ham(handPancake_big); System.out.println(handPancake_big.getName()+":"+handPancake_big.getCost()); handPancake_big = new Cucumber(handPancake_big); System.out.println(handPancake_big.getName()+":"+handPancake_big.getCost()); handPancake_big = new Bacon(handPancake_big); System.out.println(handPancake_big.getName()+":"+handPancake_big.getCost()); System.out.println("=============================="); HandPancake handPancake_mid = new HandPancake_Mid(); System.out.println("啥也不加"+handPancake_mid.getName()+":"+handPancake_mid.getCost()); handPancake_mid = new Ham(handPancake_mid); System.out.println(handPancake_mid.getName()+":"+handPancake_mid.getCost()); handPancake_mid = new Cucumber(handPancake_mid); System.out.println(handPancake_mid.getName()+":"+handPancake_mid.getCost()); handPancake_mid = new Bacon(handPancake_mid); System.out.println(handPancake_mid.getName()+":"+handPancake_mid.getCost()); System.out.println("扩展性测试:"); HandPancake handPancake_small = new HandPancake_Smalll(); System.out.println("啥也不加"+handPancake_small.getName()+":"+handPancake_small.getCost()); handPancake_small = new Egg(handPancake_small); System.out.println(handPancake_small.getName()+":"+handPancake_small.getCost()); } } 运行结果:
转载自://www.cnblogs.com/noneplus/p/11348102.html