设计模式-策略模式

折扣策略接口

public interface DiscountStrategy {
    /**
     * 计算价格
     */
    public double calcPrice(double booksPrice);
}

普通会员折扣

public class NormalStrategy implements DiscountStrategy {

    @Override
    public double calcPrice(double price) {
        System.out.println("普通会员的没有折扣");
        return price;
    }
}

中级会员折扣

public class MiddleStrategy implements DiscountStrategy {

    @Override
    public double calcPrice(double price) {
        System.out.println("中级会员9折");
        return price * 0.9;
    }
}

高级会员折扣

public class HighStrategy implements DiscountStrategy {

    @Override
    public double calcPrice(double price) {
        System.out.println("高级会员8折");
        return price * 0.8;
    }
}

价格类

public class Price {
    //持有一个具体的策略对象
    private Strategy strategy;
    /**
     * 构造函数，传入一个具体的策略对象
     * @param strategy    具体的策略对象
     */
    public Price(Strategy strategy){
        this.strategy = strategy;
    }
    
    /**
     * 计算价格
     */
    public double getFinalPrice(double price){
        return this.strategy.calcPrice(price);
    }
}

场景类

public class Client {

    public static void main(String[] args) {
        //选择并创建需要使用的策略对象
        Strategy strategy = new MiddleStrategy();
        //创建环境
        Price price = new Price(strategy);
        //计算价格
        double finalPrice = price.getFinalPrice(300);
        System.out.println("最终价格为：" + finalPrice);
    }
}