里氏转换，arraylist，path，file

1、里氏转换
1)、子类可以赋值给父类
2)、如果父类中装的是子类对象，那么可以将这个父类强转为子类对象。

  1 using System;
  2 using System.Collections.Generic;
  3 using System.Linq;
  4 using System.Text;
  5 using System.Threading.Tasks;
  6 
  7 namespace _03里氏转换练习
  8 {
  9     class Program
 10     {
 11         static void Main(string[] args)
 12         {
 13             //创建10个对象 通过一个循环 去调用他们各自打招呼的方法
 14             //Student s = new Student();
 15             //Person p = new Person();
 16             //ShuaiGuo sg = new ShuaiGuo();
 17 
 18             Person[] pers = new Person[10];
 19             Random r = new Random();
 20             for (int i = 0; i < pers.Length; i++)
 21             {
 22                 int rNumber = r.Next(1, 7);
 23                 switch (rNumber)//1-6
 24                 {
 25                     case 1: pers[i] = new Student();
 26                         break;
 27                     case 2: pers[i] = new Teacher();
 28                         break;
 29                     case 3: pers[i] = new ShuaiGuo();
 30                         break;
 31                     case 4: pers[i] = new MeiLv();
 32                         break;
 33                     case 5: pers[i] = new YeShou();
 34                         break;
 35                     case 6: pers[i] = new Person();
 36                         break;
 37                 }
 38             }
 39 
 40 
 41             for (int i = 0; i < pers.Length; i++)
 42             {
 43                // pers[i].PersonSayHi();
 44                 if (pers[i] is Student)
 45                 {
 46                     ((Student)pers[i]).StudentSayHi();
 47                   //  pers[i].PersonSayHi();
 48                 }
 49                 else if (pers[i] is Teacher)
 50                 {
 51                     ((Teacher)pers[i]).TeacherSayHi();
 52                 }
 53                 else if (pers[i] is ShuaiGuo)
 54                 {
 55                     ((ShuaiGuo)pers[i]).ShuaiGuoSayHi();
 56                 }
 57                 else if (pers[i] is YeShou)
 58                 {
 59                     ((YeShou)pers[i]).YeShouSayHi();
 60                 }
 61                 else if (pers[i] is MeiLv)
 62                 {
 63                     ((MeiLv)pers[i]).MeiLvSayHi();
 64                 }
 65                 else 
 66                 {
 67                     pers[i].PersonSayHi();
 68                 }
 69 
 70             }
 71             Console.ReadKey();
 72 
 73         }
 74     }
 75 
 76     public class Person
 77     {
 78         public void PersonSayHi()
 79         {
 80             Console.WriteLine("我是人类");
 81         }
 82     }
 83 
 84 
 85     public class Student : Person
 86     {
 87         public void StudentSayHi()
 88         {
 89             Console.WriteLine("我是学生");
 90         }
 91     }
 92 
 93     public class Teacher : Person
 94     {
 95         public void TeacherSayHi()
 96         {
 97             Console.WriteLine("我是老师");
 98         }
 99     }
100 
101 
102     public class MeiLv : Person
103     {
104         public void MeiLvSayHi()
105         {
106             Console.WriteLine("我是镁铝");
107         }
108     }
109 
110 
111     public class ShuaiGuo : Person
112     {
113         public void ShuaiGuoSayHi()
114         {
115             Console.WriteLine("我是帅锅");
116         }
117     }
118 
119 
120     public class YeShou : Person
121     {
122         public void YeShouSayHi()
123         {
124             Console.WriteLine("我是野兽");
125         }
126     }
127 
128 
129 }

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