装饰着模式（decorator）

一下代码就是运用了装饰者模式：

package com.base;

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

	public String getDescription(){
		return description;
	}

	public abstract double cost();

}

package com.base;

public abstract class CondimentDecorator extends Beverage {

	public abstract String getDescription();
}

package com.decorated;

import com.base.Beverage;

public class DarkRoast extends Beverage {

	public DarkRoast() {
		description = "Dark Roast Coffee";
	}
 
	public double cost() {
		return 0.99;
	}
}

package com.decorated;

import com.base.Beverage;

public class Espresso extends Beverage {

	public Espresso(){
		description = "Espresso";
	}
	
	@Override
	public double cost() {
		return 1.99;
	}
}

package com.decorated;

import com.base.Beverage;

public class HouseBlend extends Beverage {

	public HouseBlend(){
		description = "House Blend Coddee";
	}
	@Override
	public double cost() {
		return 0.89;
	}

}

package com.decorator;

import com.base.Beverage;
import com.base.CondimentDecorator;

public class Mocha extends CondimentDecorator {

	Beverage beverage;
	
	public Mocha(Beverage beverage){
		this.beverage= beverage;
	}
	@Override
	public String getDescription() {
		return beverage.getDescription()+", Mocha";
	}

	@Override
	public double cost() {
		return 0.20+beverage.cost();
	}

}

package com.decorator;

import com.base.Beverage;
import com.base.CondimentDecorator;

public class Soy extends CondimentDecorator {

	Beverage beverage;

	public Soy(Beverage beverage) {
		this.beverage = beverage;
	}

	public String getDescription() {
		return beverage.getDescription() + ", Soy";
	}
	
	public double cost() {
		return 0.15 + beverage.cost();
	}
}

package com.decorator;

import com.base.Beverage;
import com.base.CondimentDecorator;

public class Whip extends CondimentDecorator {

	Beverage beverage;
	 
	public Whip(Beverage beverage) {
		this.beverage = beverage;
	}
 
	public String getDescription() {
		return beverage.getDescription() + ", Whip";
	}
 
	public double cost() {
		return 0.10 + beverage.cost();
	}
}

package com.test;

import com.base.Beverage;
import com.decorated.DarkRoast;
import com.decorated.Espresso;
import com.decorated.HouseBlend;
import com.decorator.Mocha;
import com.decorator.Soy;
import com.decorator.Whip;

public class StarBuzzCoffee {
	public static void main(String args[]) {
		Beverage beverage = new Espresso();
		System.out.println(beverage.getDescription() 
				+ " $" + beverage.cost());
 
		Beverage beverage2 = new DarkRoast();
		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());
	}

}

运行结果为：

Espresso $1.99
Dark Roast Coffee, Mocha, Mocha, Whip $1.49
House Blend Coddee, Soy, Mocha, Whip $1.34

运行方式为：装饰者与被装饰者都继承相同的基类，装饰者不知道其他的装饰者的存在