设计模式入门之策略模式Strategy

//策略模式定义：//定义一些列算法，把他们一个个封装起来，并且使他们可互相交换。//本模式使得算法可独立于使用它的客户而变化//实例：对不同的客户给出不同的折扣价格，上代码//策略接口public class Strategy {public double calcPrice(double goodsPrice);}//普通用户价格算法public class NormalCustomerStrategy implements Strategy {public double calcPrice(double goodsPrice) {System.out.println("新用户、普通用户，没有折扣");return goodsPrice;}}//老用户用户价格算法public class OldCustomerStrategy implements Strategy {public double calcPrice(double goodsPrice) {System.out.println("老用户95折");return goodsPrice*(1-0.05);}}//大用户价格算法public class LargeCustomerStrategy implements Strategy {public double calcPrice(double goodsPrice) {System.out.println("大用户9折");return goodsPrice*(1-0.1);}}//上下文（环境），价格管理public class Price {private Strategy strategy = null;public Price(Strategy strategy) {this.strategy = strategy;}public double calcPrice(double goodsPrice) {return this.strategy.calcPrice(goodsPrice);}}//测试public class Client {Strategy strategy = new LargeCustomerStrategy();Price ctx = new Price(strategy);ctx.calcPrice(1000);}//策略模式本质：封装算法//优点：定义一系列算法，便于扩展；可以避免多重条件语句，更好的扩展性//缺点：客户必须了解每种策略的不同；增加了对象数目