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  • JAVA设计模式---装饰者模式

    写在前面的话:

      该模式动态的将责任附加到对象上,若要扩展功能,装饰者提供了比继承更有弹性的替代方案。装饰者可以在被装饰者的行为前面与/或后面加上自己的行为,甚至将被装饰者的行为整个取代掉,而达到特定的目的。

      该模式的实现意味着一群装饰者类,这些类反映出被装饰的组件类型,用来包装具体组件。

          缺点在于,可以用无数个装饰者包装一个组件,但会导致设计中出现许多小对象,如果过度引用,会让程序变得很复杂。

    案例分析:

    需求:模拟 StarbuzzCoffee 的订单系统,咖啡原种类为Espresso,HouseBlend,添加调料种类分别为Soy,Mocha,Whip,对应不同的收费,杯子分为大中小三种,分别对应不同的收费

    代码实现:

    1)咖啡部分:

    public abstract class Beverage {
        String description = "Unknown Beverage";
    
        public String getDescription(){
            return description;
        }
    
        public abstract double cost();
    }
    public class Espresso extends Beverage {
        public Espresso() {
            description = "Espresso";
        }
    
        @Override
        public double cost() {
            return 1.99;
        }
    }
    
    public class HouseBlend extends Beverage {
        public HouseBlend() {
            description = "HouseBlend";
        }
    
        @Override
        public double cost() {
            return 0.89;
        }
    }

    2)调料部分:

    public abstract class CondimentBeverage extends Beverage {
        public abstract String getDescription();
    }
    
    public class Soy extends CondimentBeverage {
        Beverage beverage;
    
        public Soy(Beverage beverage) {
            this.beverage = beverage;
        }
    
        @Override
        public String getDescription() {
            return beverage.getDescription();
        }
    
        @Override
        public double cost() {
            return 0.30+beverage.cost();
        }
    }
    
    public class Mocha extends CondimentBeverage {
        Beverage beverage;
    
        public Mocha(Beverage beverage) {
            this.beverage = beverage;
        }
    
        @Override
        public String getDescription() {
            return beverage.getDescription();
        }
    
        @Override
        public double cost() {
            return 0.20+beverage.cost();
        }
    }
    
    public class Whip extends CondimentBeverage {
        Beverage beverage;
    
        public Whip(Beverage beverage) {
            this.beverage = beverage;
        }
    
        @Override
        public String getDescription() {
            return beverage.getDescription();
        }
    
        @Override
        public double cost() {
            return 0.40+beverage.cost();
        }
    }
    

     3) 杯子选择:

    public abstract class Size extends Beverage {
        public abstract String getDescription();
    }
    
    public class BigSize extends Size {
        Beverage beverage;
    
        public BigSize(Beverage beverage) {
            this.beverage = beverage;
        }
    
        @Override
        public String getDescription() {
            return beverage.getDescription();
        }
    
        @Override
        public double cost() {
            return 0.30+beverage.cost();
        }
    }
    
    public class MiddleSize extends Size {
        Beverage beverage;
    
        public MiddleSize(Beverage beverage) {
            this.beverage = beverage;
        }
    
        @Override
        public String getDescription() {
            return beverage.getDescription();
        }
    
        @Override
        public double cost() {
            return 0.20+beverage.cost();
        }
    }
    
    public class SmalleSize extends Size {
        Beverage beverage;
    
        public SmalleSize(Beverage beverage) {
            this.beverage = beverage;
        }
    
        @Override
        public String getDescription() {
            return beverage.getDescription();
        }
    
        @Override
        public double cost() {
            return 0.10+beverage.cost();
        }
    }
    

     4)测试代码---生产订单:

    public class StarbuzzCoffee {
        public static void main(String[] args) {
            Beverage beverage1 = new Espresso();   //订一杯Espresso,不添加任何调料
            System.out.println(beverage1.getDescription()+":$"+beverage1.cost());
    
            Beverage beverage2 = new HouseBlend();   //订一杯HouseBlend,不添加任何调料
            beverage2 = new Mocha(beverage2);
            beverage2 = new Mocha(beverage2);   //两份摩卡
            System.out.println(beverage2.getDescription()+"(double Mocha):$"+beverage2.cost());
    
            beverage2 = new Soy(beverage2);     //再加一份soy
            System.out.println(beverage2.getDescription()+"(additional Soy):$"+beverage2.cost());
    
            beverage2 = new Whip(beverage2);     //再加一份whip
            System.out.println(beverage2.getDescription()+"(additional Whip):$"+beverage2.cost());
    
            beverage2 = new MiddleSize(beverage2);   //选择中杯
            System.out.println(beverage2.getDescription()+"(choose middleSize):$"+beverage2.cost());
        }
    }
    

     测试结果:

    Espresso:$1.99
    HouseBlend(double Mocha):$1.29
    HouseBlend(additional Soy):$1.59
    HouseBlend(additional Whip):$1.99
    HouseBlend(choose middleSize):$2.19

     

     

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  • 原文地址:https://www.cnblogs.com/hunterCecil/p/5676346.html
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