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策略模式

eg:

public interface MemberStrategy {
    /**
     * 计算图书的价格
     * @param booksPrice    图书的原价
     * @return    计算出打折后的价格
     */
    public double calcPrice(double booksPrice);
}
  • 策略1
public class PrimaryMemberStrategy implements MemberStrategy {

    @Override
    public double calcPrice(double booksPrice) {
        System.out.println("对于初级会员的没有折扣");
        return booksPrice;
    }

}
  • 策略2
public class IntermediateMemberStrategy implements MemberStrategy {

    @Override
    public double calcPrice(double booksPrice) {

        System.out.println("对于中级会员的折扣为10%");
        return booksPrice * 0.9;
    }

}
  • 策略3
public class AdvancedMemberStrategy implements MemberStrategy {

    @Override
    public double calcPrice(double booksPrice) {

        System.out.println("对于高级会员的折扣为20%");
        return booksPrice * 0.8;
    }
}

价格类

public class Price {
    //持有一个具体的策略对象
    private MemberStrategy 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(MemberStrategy strategy){
        this.strategy = strategy;
    }

    /**
     * 计算图书的价格
     * @param booksPrice    图书的原价
     * @return    计算出打折后的价格
     */
    public double quote(double booksPrice){
        return this.strategy.calcPrice(booksPrice);
    }
}

客户端自主选择合适的策略

public class Client {

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

}

应用

Java spi(Service Provider Interface)机制

Java SPI 实际上是“基于接口的编程+策略模式+配置文件”组合实现的动态加载机制。

Copyright @doctording all right reserved,powered by Gitbook该文件修改时间: 2020-12-24 10:14:32

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