装饰者模式案例

阳光穿透心脏的1/2处 2022-06-18 04:20 86阅读 0赞

在不必改变原类文件和使用继承的情况下，动态地扩展一个对象的功能。它是通过创建一个包装对象，也就是装饰来包裹真实的对象。

拿一个咖啡对象，以摩卡对象来装饰它，以奶泡对象来装饰它，调用cost方法，并依靠委托将调料的价格加进去

public abstract class Beverage \{  
    //原味类  
    //默认包访问权限  
    String description="Unknown Beverage";  
    public String getDescription()\{  
        return description;  
    \}  
    public abstract double cost();  
\}  
  
//调料基础类  
public abstract class CondimentDecorator extends Beverage\{  
    public abstract String getDescription();  
\}  
  
//一种饮料  
public class Espresso extends Beverage\{  
    public Espresso()\{  
        description="Espresso";  
    \}  
    @Override  
    public double cost() \{  
        // TODO Auto-generated method stub  
        return 1.99;  
    \}  
  
\}  
  
//一种饮料  
public class HouseBlend extends Beverage\{  
    public HouseBlend()\{  
        description="House Blend Coffee";  
    \}  
    @Override  
    public double cost() \{  
        // TODO Auto-generated method stub  
        return 0.89;  
    \}  
  
\}  
  
//一种调料  
public class Mocha extends CondimentDecorator\{  
    Beverage beverage;  
    public Mocha(Beverage beverage)\{  
        this.beverage=beverage;  
    \}  
    @Override  
    public String getDescription() \{  
        // TODO Auto-generated method stub  
        return beverage.getDescription()+",Mocha";  
    \}  
  
    @Override  
    public double cost() \{  
        // TODO Auto-generated method stub  
        return 0.20+beverage.cost();  
    \}  
  
\}  
  
public class Soy extends CondimentDecorator\{  
    Beverage beverage;  
    public Soy(Beverage beverage)\{  
        this.beverage=beverage;  
    \}  
    @Override  
    public String getDescription() \{  
        // TODO Auto-generated method stub  
        return beverage.getDescription()+",Soy";  
    \}  
  
    @Override  
    public double cost() \{  
        // TODO Auto-generated method stub  
        return 0.20+beverage.cost();  
    \}  
  
\}

public class Whip extends CondimentDecorator\{  
    Beverage beverage;  
    public Whip(Beverage beverage)\{  
        this.beverage=beverage;  
    \}  
    @Override  
    public String getDescription() \{  
        // TODO Auto-generated method stub  
        return beverage.getDescription()+",Whip";  
    \}  
  
    @Override  
    public double cost() \{  
        // TODO Auto-generated method stub  
        return 0.20+beverage.cost();  
    \}  
  
\}  
  
测试：

public class MyTest \{  
  
    public static void main(String\[\] args) \{  
        // TODO Auto-generated method stub  
        Beverage beverage=new Espresso();//订了一杯Espresso，不需要调料，打印出它的描述与价格  
        System.out.println(beverage.getDescription()+" $"+beverage.cost());  
        Beverage beverage2=new Espresso();  
        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());  
    \}  
  
\}

效果：

Espresso $1.99  
Espresso,Mocha,Mocha,Whip $2.5900000000000003  
House Blend Coffee,Soy,Mocha,Whip $1.49