设计模式（一）--装饰模式

 装饰模式：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替代方案
* 1）装饰者和被装饰者有相同的超类型
* 2）装饰者可以在所委托被装饰者的行为之前/之后，加上自己的行为，以达到特定的目的。

/**
 * Created by wqc on 2017/10/14.
 * 饮料的超类：只包含饮料的描述方法description和计算价格的方法cost
 */
public abstract  class Beverage {
    String description = "Unknown Beverage";

    public String getDescription()
    {
        return description;
    }

    public abstract double cost();
}

/**
 * Created by wqc on 2017/10/14.
 * 装饰者--调料的超类:所有的调料都需重新描述方法
 */
public abstract class CondimentDecorator extends Beverage{
    public abstract String getDescription();
}

/**
 * Created by wqc on 2017/10/14.
 * 装饰者:调料--摩卡
 */
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 beverage.cost()+0.20;
    }
}

/**
 * Created by wqc on 2017/10/14.
 * 装饰者：调料--豆浆
 */
public class Soy extends CondimentDecorator {
    Beverage beverage;
    public Soy(Beverage beverage)
    {
        this.beverage = beverage;
    }
    @Override
    public String getDescription() {
        return beverage.getDescription()+",Soy";
    }

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

/**
 * Created by wqc on 2017/10/14.
 * 被装饰者：饮料的实现类--溶缩咖啡
 */
public class Espresso extends Beverage{

    public Espresso()
    {
        description = "Espresso";
    }
    @Override
    public double cost() {
        return 1;
    }
}

/**
 * Created by wqc on 2017/10/14.
 * 装饰模式：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替代方案
 * 1）装饰者和被装饰者有相同的超类型
 * 2）装饰者可以在所委托被装饰者的行为之前/之后，加上自己的行为，以达到特定的目的。
 */
public class test {
    public static void main(String[] args) {
        Beverage beverage = new Espresso();
        System.out.println(beverage.getDescription()+"---"+beverage.cost());

        beverage = new Soy(beverage);
        System.out.println(beverage.getDescription()+"---"+beverage.cost());

        beverage = new Mocha(beverage);
        System.out.println(beverage.getDescription()+"---"+beverage.cost());

    }
}