设计模式-装饰器模式

UML

代码

// 咖啡接口  
interface Coffee {  String getDescription();  double cost();  
}  // 浓缩咖啡  
class Espresso implements Coffee {  @Override  public String getDescription() {  return "Espresso";  }  @Override  public double cost() {  return 1.99;  }  
}  // 装饰器抽象类  
abstract class CoffeeDecorator implements Coffee {  protected Coffee decoratedCoffee;  public CoffeeDecorator(Coffee decoratedCoffee) {  this.decoratedCoffee = decoratedCoffee;  }  @Override  public String getDescription() {  return decoratedCoffee.getDescription();  }  @Override  public double cost() {  return decoratedCoffee.cost();  }  
}  // 牛奶装饰器  
class Milk extends CoffeeDecorator {  public Milk(Coffee decoratedCoffee) {  super(decoratedCoffee);  }  @Override  public String getDescription() {  return decoratedCoffee.getDescription() + ", Milk";  }  @Override  public double cost() {  return decoratedCoffee.cost() + 0.10;  }  
}  // 糖装饰器  
class Sugar extends CoffeeDecorator {  public Sugar(Coffee decoratedCoffee) {  super(decoratedCoffee);  }  @Override  public String getDescription() {  return decoratedCoffee.getDescription() + ", Sugar";  }  @Override  public double cost() {  return decoratedCoffee.cost() + 0.10;  }  
}  // 使用  
public class CoffeeOrder {  public static void main(String[] args) {  Coffee espresso = new Espresso();  Coffee espressoWithMilk = new Milk(espresso);  Coffee espressoWithMilkAndSugar = new Sugar(espressoWithMilk);  System.out.println(espressoWithMilkAndSugar.getDescription() + " $" + espressoWithMilkAndSugar.cost());  }  
}// 输出结果：Espresso, Milk, Sugar $2.19