OO设计模式03—装饰者模式

OO设计模式—装饰者模式

设计原则tip：类应该对拓展开放，对修改关闭。（在不修改现有代码的情况下，就可搭配新的行为）

装饰者模式：动态地将责任附加到对象上。若要拓展功能，装饰者提供了比继承更有弹性的替代方案。

以下是《模式设计》书中的星巴克咖啡例子：

public abstract class Beverage
{
	String description = "Unknown Beverage";

	public String getDescription(){
	
		return description;
	}
	public abstract double cost();
}

public abstract class CondimentDecorator extends Beverage   //咖啡的调料，所有调料装饰者必须覆写getDescription方法
{
	public abstract String getDescription();
}

//一些基本饮品，作为基本组件

public class Espresso extends Beverage
{
	public Espresso(){
	
		description = "Espresso";

	}
	public double cost(){
	
		return 1.99;

	}
}

public class HouseBlend extends Beverage
{
	public HouseBlend(){
	
		description = "HouseBlend";

	}
	public double cost(){
	
		return .98;
	}

}

//以下为调料，作为装饰者

public class Mocha extends CondimentDecorator
{
	Beverage beverage;

	public Mocha(Beverage beverage){
	
		this.berverage = berverage;
	}
	public String getdDescription(){
	
		return berverage.getDescription();
	}
	public double cost(){
	
		return .20 + berverage.cost();
	}
}
//测试代码

public class StarbuzzCoffee
{
	public static void main(String[] args){
	
		Berverage beverage = new Espresso();
		System.out.println(berverage.getDescription()+ "$" +berverage.cost());

		Berverage beverage2 = new HouseBlend();
		beverage2 = new Mocha(beverage2);
		beverage2 = new Mocha(beverage2);
		beverage2 = new Whip(beverage2);	//添加调料
		System.out.println(berverage.getDescription()+"$"+berverage.cost());
		
	}

}