设计模式——装饰者模式

package Decorator_pattern;

/*
 * 这里举一个简单的例子：披萨都是由一个抽象的Food然后实例出的原味Pizza来代表和上面可以加辅料如香肠和蔬菜组成，香肠和蔬菜
 * 同样属于食物所以可以继承自Food。
 */

abstract class Food {
	String description = "我能吃";
	public String getDescription() {
		return description;
	}
	public abstract double cost();
}



abstract class Flavour extends Food {   // 披萨上的一些辅料作为修饰
	public abstract String getDescription();
}

class Pizza extends Food {
	public Pizza() {
		description = "披萨";
	}
	@Override
	public double cost() {
		return 2.6;
	}
}

class Sausage extends Flavour {
	Food food;
	
	public Sausage(Food food) {
		this.food = food;
	}

	@Override
	public String getDescription() {
		return "香肠" + this.food.getDescription();
	}

	@Override
	public double cost() {
		return this.food.cost() + 1.2;
	}	
}

class Vegetable extends Flavour {
	Food food;
	public Vegetable(Food food) {
		this.food = food;
	}
	@Override
	public String getDescription() {
		return "蔬菜" + this.food.getDescription();
	}
	@Override
	public double cost() {
		return this.food.cost() + 1.1;
	}
}

// 测试代码 
public class Main {
	public static void main(String args[]) {
		Food food = new Pizza();
		System.out.println("初始就是一个原味的披萨");
		System.out.println(food.getDescription() + " " + food.cost());
		food = new Sausage(food);
		System.out.println("加了一份香肠之后");
		System.out.println(food.getDescription() + " " + food.cost());
		food = new Vegetable(food);
		System.out.println("加了一份蔬菜之后");
		System.out.println(food.getDescription() + " " + food.cost());
		
	}
}