Javaデザインパターンにおける戦略パターンと状態パターンの分析例

/// 
 /// 用户账号信息 /// 
 public abstract class Account { /// 
 /// 账号 /// 
 private string account; /// 
 /// 密码 /// 
 private string pwd; public abstract decimal getBalance(decimal d); }

/// 
 /// 冻结账户类 /// 
 public class DeadAccount:Account { public override decimal getBalance(decimal d) { return 0; } }

/// 
 /// 激活账户类 /// 
 public class ActiveAccount:Account { public override decimal getBalance(decimal d) { return d; } }

/// 
 /// 交易类 负责用户交易处理的类 /// 
 public class Trade { /// 
 /// 保存用户账号信息 /// 
 private Account account; public Account VolidateLogin(Account a) { //query the database to validate the user exists //For Example this.account = new DeadAccount(); return this.account; } /// 
 /// 商业逻辑 取款 /// 
 ///  ///  public decimal GetBalance(decimal d) { return this.account.getBalance(d); } }

/// 
 /// 取款人 /// 
 public class User { /// 
 /// 用户账号信息 /// 
 private Account account; /// 
 /// 交易处理类 /// 
 private Trade trade; public User(Account a, Trade t) { this.account = a; tthis.trade = t; } /// 
 /// 用户登录类 /// 
 public void Login() { trade.VolidateLogin(account); } /// 
 /// 取款 /// 
 ///  ///  public decimal GetBalance(decimal d) { return trade.GetBalance(d); } }

class Client { static void Main(string[] args) { //开始用户取款，默认是激活账户 ActiveAccount aa = new ActiveAccount(); Trade t = new Trade(); User u = new User(aa,t); //先登录，后取款 u.Login(); Console.WriteLine(u.GetBalance(100)); Console.ReadLine(); } }

/// 
 /// 具体商品类 /// 
 public class goods { /// 
 /// 商品类型 /// 
 public string Type { set; get; } /// 
 /// 商品名称 /// 
 public string Name { get; set; } /// 
 /// 商品价格 /// 
 public decimal Price { get; set; } }

/// 
 /// 抽象策略接口 /// 
 public interface IDiscountStrategy { decimal GetDiscount(goods g); }

/// 
 /// 秋装打折策略 /// 
 public class AutumnDressDiscountStrategy:IDiscountStrategy { #region IDiscountStrategy Members public decimal GetDiscount(goods g) { return (decimal)0.9 * g.Price; } #endregion } /// 
 /// 运动鞋打折策略 /// 
 public class SportShoesDiscountStrategy:IDiscountStrategy { #region IDiscountStrategy Members public decimal GetDiscount(goods g) { return g.Price * (decimal)0.8; } #endregion }

/// 
 /// 收银台 /// 
 public class CashierDesk { /// 
 /// 购物车 /// 
 private ShoppingCar shoppingCar; /// 
 /// 策略字典 /// 
 private Dictionary strategies; public CashierDesk(ShoppingCar sc, Dictionary s) { this.shoppingCar = sc; this.strategies = s; } /// 
 /// 获得所有商品的价格 /// 
 ///  public decimal GetTotalPrice() { return shoppingCar.GoodsList.Sum(p => p.Price); } /// 
 /// 获得所有商品的总的折扣 /// 
 ///  public decimal GetTotalDiscount() { decimal sum = 0; IDiscountStrategy idiscountStrategy; foreach (goods g in shoppingCar.GoodsList) { idiscountStrategy=strategies.SingleOrDefault(p => p.Key == g.Type).Value; if (idiscountStrategy != null) { sum += idiscountStrategy.GetDiscount(g); } } return sum; } }

class Client { static void Main(string[] args) { ShoppingCar sc = new ShoppingCar(); Dictionary discountD = new Dictionary(); //向购物车中加入商品 sc.AddGoods(new goods {Name="NIKE鞋 ",Price=100,Type="运动鞋" }); sc.AddGoods(new goods { Name = "秋装", Price = 200, Type = "秋装" }); sc.AddGoods(new goods { Name = "苹果", Price = 300, Type = "水果" }); //配置折扣策略 discountD.Add("运动鞋", new SportShoesDiscountStrategy()); discountD.Add("秋装", new AutumnDressDiscountStrategy()); CashierDesk cd = new CashierDesk(sc, discountD); //得到所有商品总价 Console.WriteLine(cd.GetTotalPrice()); //得到所有商品折扣价 Console.WriteLine(cd.GetTotalDiscount()); Console.ReadLine(); } }