装饰者模式

参考java设计模式

装饰者模式 动态的将责任附加到对象上，若要扩展功能，装饰者提供比继承更有弹性的代替方案

类图：

举例：一杯茶，有绿茶、红茶、通过装饰者模式变成蜂蜜绿茶，加糖绿茶

上代码：

package Decorator;

/**
 * 茶的抽象类
 */
public abstract class AbstractTea {
    protected String description = "unkown Tea";

    public String getDescription(){
        return description;
    }

    public abstract double cost();
}

package Decorator;

/**
 * 红茶
 */
public class BlackTea extends AbstractTea{

    public BlackTea() {
        this.description = "红茶";
    }

    @Override
    public double cost() {
        return 5;
    }
}

package Decorator;

/**
 * 绿茶
 */
public class GreenTea extends AbstractTea{

    public GreenTea() {
        this.description = "绿茶";
    }

    @Override
    public double cost() {
        return 3;
    }
}

茶的装饰者： 可以做成蜂蜜绿茶 白糖绿茶

package Decorator;

public abstract class TeaDecoraotr extends AbstractTea {

    public abstract String getDescription();

}

package Decorator;

/**
 * 加蜂蜜的茶
 */
class AddHoneyTeaDecorator extends TeaDecoraotr {
    AbstractTea abstractTea;

    public  AddHoneyTeaDecorator(AbstractTea abstractTea){
        this.abstractTea = abstractTea;
    }

    @Override
    public String getDescription() {
        return abstractTea.getDescription() + " 加蜂蜜";
    }

    @Override
    public double cost() {
        return abstractTea.cost() + 2;
    }
}

package Decorator;

/**
 * 加糖的茶
 */
public class AddSugerTeaDecorator extends TeaDecoraotr {
    AbstractTea abstractTea;

    public  AddSugerTeaDecorator(AbstractTea abstractTea){
         this.abstractTea = abstractTea;
    }

    @Override
    public String getDescription() {
        return abstractTea.getDescription() + " 加糖";
    }

    @Override
    public double cost() {
        return abstractTea.cost() + 0.3;
    }
}

package Decorator;

import com.sun.scenario.effect.impl.sw.sse.SSEBlend_SRC_OUTPeer;

public class DecoratorTest {
    public static void main(String[] args) {
        AbstractTea blackTea = new BlackTea();
        System.out.println("一杯  "+blackTea.getDescription()+" 共计"+blackTea.cost()+"元");

        AbstractTea greeTea = new GreenTea();
        System.out.println("一杯  "+greeTea.getDescription()+" 共计"+greeTea.cost()+"元");

        AbstractTea addHoneyGreenTea = new AddHoneyTeaDecorator(greeTea);
        System.out.println("一杯  "+addHoneyGreenTea.getDescription()+" 共计"+addHoneyGreenTea.cost()+"元");

        AbstractTea addSuggrGreenTea = new AddSugerTeaDecorator(greeTea);
        System.out.println("一杯  "+addSuggrGreenTea.getDescription()+" 共计"+addSuggrGreenTea.cost()+"元");


    }
}

输出：

一杯  红茶 共计5.0元
一杯  绿茶 共计3.0元
一杯  绿茶 加蜂蜜 共计5.0元
一杯  绿茶 加糖 共计3.3元