c进一步学习类与对象

第九周进一步学习面向对象

代码阅读：Times类案例Time类

classTime{privateinthour,minute,second;publicvoidSetTime(inthour,intminute,intsecond){

//this表示当前对象

this.hour=hour;this.minute=minute;this.second=second;}publicstringToUniversalString(){returnstring.Format("{0:d2}:{1:d2}:{2:d2}",hour,minute,second);}publicoverridestringToString(){intstandardHour=(hour==0||hour==12?12:hour%12);stringpostfix=hour<12?"AM":"PM";returnstring.Format("{0:d2}:{1:d2}:{2:d2}{3}",standardHour,minute,second,postfix);}}代码阅读：Times类案例(续)TimeTest类classTimeTest{staticvoidMain(string[]args){Timet1=newTime();Console.WriteLine(t1.ToUniversalString());Console.WriteLine(t1.ToString());t1.SetTime(13,27,6);Console.WriteLine(t1.ToUniversalString());Console.WriteLine(t1.ToString());}}代码改进1：添加数据合法性验证在Time类中为hour，minute，second添加数据合法性验证

publicintHour{get{returnhour;}//只能在类中对属性进行赋值

privateset{hour=(value>0&&value<=24?value:0);}}publicintMinute{get{returnminute;}privateset{minute=value>0&&value<=60?value:0;}}publicintSecond{get{returnsecond;}privateset{second=value>0&&value<=60?value:0;}}publicvoidSetTime(inth,intmints){//this表示当前对象

this.Hour=h;

this.Minute=m;

this.Second=s;}代码改进2：添加构造函数在Time类中添加多个构造函数，多种方式初始化时间

publicTime(inth,intm,ints){SetTime(h,m,s);}

//观察在类中如何调用构造函数

publicTime(inth,intm):this(h,m,0){}publicTime(inth):this(h,0,0){}publicTime():this(0,0,0){}publicTime(Timet):this(t.Hour,t.Minute,t.Second){}代码改进2：使用重载构造函数在Time类中添加多个构造函数，多种方式初始化时间

staticvoidMain(string[]args){Timet1=newTime();Timet2=newTime(2);Timet3=newTime(21,34);Timet4=newTime(12,25,42);Timet5=newTime(27,74,99);Timet6=newTime(t4);Console.WriteLine("t1:");Console.WriteLine(t1.ToUniversalString());Console.WriteLine(t1.ToString());}代码改进3：添加索引器通过索引器，我们可以像访问数组元素一样访问对象的成员。

//用this定义属性式的类成员，称为索引器

publicintthis[intindex]{get{switch(index){case0:returnhour;

case1:returnminute;case2:returnsecond;

default:return-1;}}set{switch(index){case0:Hour=value;break;case1:Minute=val