JAVA设计模式(7)结构型-装饰器模式

装饰器模式 允许向一个现有的对象添加新的功能，同时又不改变其结构。装饰者可以在所委托被装饰者的行为之前或之后加上自己的行为，以达到特定的目的。

//author： V：jbossjf
package DesignPattern.Strategy.Decorator;

public interface Drink {
    public float cost();
    public String getDescription();
}

package DesignPattern.Strategy.Decorator;

public class Coffee implements Drink {
    final private String description = "coffee";
    //每杯 coffee 售价 10 元
    public float cost() {
        return 10;
    }

    public String getDescription() {
        return description;
    }
}

package DesignPattern.Strategy.Decorator;

public abstract class CondimentDecorator implements Drink {
    protected Drink decoratorDrink;

    public CondimentDecorator(Drink decoratorDrink) {
        this.decoratorDrink = decoratorDrink;
    }

    public float cost() {
        return decoratorDrink.cost();
    }

    public String getDescription() {
        return decoratorDrink.getDescription();
    }
}

package DesignPattern.Strategy.Decorator;

public class Milk extends CondimentDecorator {
    public Milk(Drink decoratorDrink) {
        super(decoratorDrink);
    }

    @Override
    public float cost() {
        return super.cost() + 2;
    }

    @Override
    public String getDescription() {
        return super.getDescription() + " milk";
    }
}

package DesignPattern.Strategy.Decorator;

public class Sugar extends CondimentDecorator {
    public Sugar(Drink decoratorDrink) {
        super(decoratorDrink);
    }

    @Override
    public float cost() {
        return super.cost() + 1;
    }

    @Override
    public String getDescription() {
        return super.getDescription() + " sugar";
    }
}

package DesignPattern.Strategy.Decorator;

public class CoffeeShop {
    public static void main(String[] args) {
        //点一杯coffee
        Drink drink = new Coffee();
        System.out.println(drink.getDescription() + ":" + drink.cost());
        //加一份奶
        drink = new Milk(drink);
        System.out.println(drink.getDescription() + ":" + drink.cost());
        //加一份糖
        drink = new Sugar(drink);
        System.out.println(drink.getDescription() + ":" + drink.cost());
        //再加一份糖
        drink = new Sugar(drink);
        System.out.println(drink.getDescription() + ":" + drink.cost());
    }
}