1、什么是面向对象

面向对象(Object Oriented)是软件开发方法。面向对象是相对于面向过程来讲的，面向对象方法，把相关的数据和方法组织为一个整体来看待，从更高的层次来进行系统建模，更贴近事物的自然运行模式。

2、类的使用

C#和JAVA的语法基本类似，后续先以C#的语法为例子。

2.1 定义类简单的例子

定义一个运动员，包含姓名和国家，以及参加比赛的内容，并添加一个空的构造函数和一个初始赋值的构造函数

public class Sportsman{    public String? Name { get; set; }    public String? Country { get; set; }    //构造函数    public Sportsman()    {    }    //构造函数方式1    public Sportsman(String name, String country)    {        Name = name;        Country = country;    }    public void Competition()    {        Console.WriteLine("I participate in the competition");    }    public void CompetitionMoreInfo()    {        Console.WriteLine($"{Country} {Name} participate in the competition");    }}class demo {     static void Main(string[] args)    {        Sportsman sportsman = new Sportsman();        sportsman.Competition();        Sportsman sportsman2 = new Sportsman("Niu","China");        sportsman2.CompetitionMoreInfo();    }}

简单的输出为：

2.2类继承一下再使用

当声明一个子类对象时，构造函数的执行顺序为–先执行父类的→再执行子类的。子类可以通过 base 关键字代表父类调用父类构造

public class Sportsman{    public String? Name { get; set; }    public String? Country { get; set; }   // 构造函数    public Sportsman() {        Console.WriteLine("Sportsman默认构造函数");    }    //构造函数方式1    public Sportsman(String name, String country){        Name = name;        Country = country;        Console.WriteLine("Sportsman赋值的构造函数");    }    public void Competition() {        Console.WriteLine("I participate in the competition");    }    public void CompetitionMoreInfo() {        Console.WriteLine($"{Country} {Name} participate in the competition");    }}public class Runner : Sportsman{    public void RunForHappy() {        Console.WriteLine("Running For Happy");     }}public class Swimmer : Sportsman{    public Swimmer(string name, string country) : base(name, country) {        Console.WriteLine("Swimmer的构造函数");    }    public void LoveWater(){        Console.WriteLine("I am LoveWater");    }}class demo {     static void Main(string[] args)    {        Sportsman sportsman = new Sportsman();        sportsman.Competition();        Sportsman sportsman2 = new Sportsman("Niu", "China");        sportsman2.CompetitionMoreInfo();        Runner runner = new Runner();        runner.Competition();        runner.RunForHappy();        Swimmer swimmer = new Swimmer("Li", "China");        swimmer.Competition();        swimmer.CompetitionMoreInfo();        swimmer.LoveWater();    }}

简单的输出为：

2.3类继承的好处

（1）抽象出共同特征，反复使用。做到Don't Repeat yourself。

（2）通过子类继承父类，扩展了功能

3.其它

以后有空再完善内容。