68 C#教程-面向对象的封装性

 Player p1 = new Player(2000, "张三", 20, 2, 100);

      Player p2 = new Player(2001, "李四", 50, 1, 100);

      Console.WriteLine(p1.atk);

      p1.showInfos();

      p2.showInfos();

      p1.minusHp(p2.atk);

 public class Player

  {

    public int id;

    public string name;

    public int atk;

    public int def;

    public int hp;

    public Player(int id,string name,int atk,int def,int hp)

    {

    }

    public void minusHp(int atk)

    {

      int dmg = atk - def;

      hp=hp-dmg;

      Console.WriteLine(hp);

    }

    public void showInfos()

    {

      string info = "";

      info = info + "名字：" + name + "\n"; 

      info = info + "id：" + id + "\n";

      info = info + "攻击力：" + atk + "\n";

      info = info + "防御力：" + def + "\n";

      info = info + "血量：" + hp + "\n";

      Console.WriteLine(info);

    }

  }

但实际打印出来的全部是0.这是为啥。。