0725异常保护和类

           

      一.  异常保护

             ////try
            ////catch
            //try //保护可能出错的语句
            //{
            //    Console.Write("请输入一个整数：");
            //    int a = int.Parse(Console.ReadLine());
            //    Console.WriteLine("您的输入正确。");
            //}
            //catch //若try的语句有问题，会直接抓住，到这个位置执行
            //{
            //    Console.WriteLine("您的输入有误！");
            //}
            //finally //最后要做什么，写与不写一样
            //{
            //    Console.WriteLine("感谢您的使用，再见！");
            //}
            //Console.ReadLine();

二.类 

1.String类
            //string s = "   abCDefgb   ";
            ////int a = s.Length;//获取长度
            //Console.WriteLine(s.Length);

            ////去掉前后空格
            //Console.Write(s.Trim());
            ////只去掉前面的空格
            //Console.Write(s.TrimStart());
            //Console.WriteLine(123);
            ////只去掉后面的空格
            //Console.Write(s.TrimEnd());

            ////将全部小写字母转换为大写
            //Console.WriteLine(s.ToUpper());
            ////将所有大写字母转换为小写
            //Console.WriteLine(s.ToLower());

            ////返回第一次出现该字符或字符串的索引号
            ////注意：索引号是从0开始
            ////返回值为-1.表示没有找到该字符或字符串
            //Console.WriteLine(s.IndexOf("abc"));
            ////返回最后一次出现该字符或字符串的索引号
            //Console.WriteLine(s.LastIndexOf("b"));

            ////substring截取字符串
            ////写一个参数的时候，表示从这个索引号开始截取，一直到最后
            //Console.WriteLine(s.Substring(3));
            ////两个参数表示，从哪个位置开始截取，截取多长
            //Console.WriteLine(s.Substring(4,4));

            ////startswith    是否以**字符串开头
            //Console.WriteLine(s.StartsWith("ab"));
            ////endswith      是否以**字符串结尾
            //Console.WriteLine(s.EndsWith("b"));

            ////contains      是否包含
            //Console.WriteLine(s.Contains("CD"));

            ////replace       替换
            //Console.WriteLine(s.Replace("b","BB"));

            //Console.WriteLine(s);

            //Console.ReadLine();

            //请输入您的身份证号，为您截取出来您的生日
            //370321199003053330
            //Console.Write("请输入您的身份证号：");
            //string cid = Console.ReadLine();
            //string year = cid.Substring(6,4);
            //string month = cid.Substring(10,2);
            //string day = cid.Substring(12,2);
            //Console.WriteLine("您的出生日期为：{0}年{1}月{2}日。",year,month,day);
            //Console.ReadLine();

            //练习：判断邮箱格式是否正确
            //1.有且只能有一个@
            //2.不能以@开头
            //3.@之后至少有一个.
            //4.@和.不能靠在一起
            //5.不能以.结尾
            //Console.Write("请输入您的邮箱账号：");
            //string mail = Console.ReadLine();
            //if (mail.Contains("@"))
            //{
            //    int a = mail.IndexOf("@");
            //    int b = mail.LastIndexOf("@");
            //    if (a == b)
            //    {
            //        if (!mail.StartsWith("@"))
            //        {
            //            string mail1 = mail.Substring(a);
            //            if (mail1.Contains("."))
            //            {
            //                int c = mail1.IndexOf(".");
            //                if (c != 1)
            //                {
            //                    if (mail.Substring(a - 1, 1) != ".")
            //                    {
            //                        if (!mail.EndsWith("."))
            //                        {
            //                            Console.WriteLine("邮箱格式正确，您输入的邮箱账号是："+mail);
            //                        }
            //                        else
            //                        {
            //                            Console.WriteLine("您的邮箱格式不正确！");                                   
            //                        }
            //                    }
            //                    else
            //                    {
            //                        Console.WriteLine("您的邮箱格式不正确！");                                   
            //                    }
            //                }
            //                else
            //                {
            //                    Console.WriteLine("您的邮箱格式不正确！");                               
            //                }
            //            }
            //            else
            //            {
            //                Console.WriteLine("您的邮箱格式不正确！");
            //            }
            //        }
            //        else
            //        {
            //            Console.WriteLine("您的邮箱格式不正确！");
            //        }
            //    }
            //    else
            //    {
            //        Console.WriteLine("您的邮箱格式不正确！");
            //    }
            //}
            //else
            //{
            //    Console.WriteLine("您的邮箱格式不正确！");
            //}

            //Console.ReadLine();

    2.Math类    数学类
            ////ceiling    天花板   取上线
            //Console.WriteLine(Math.Ceiling(4.4));
            ////floor     地板      取下线
            //Console.WriteLine(Math.Floor(4.4));
            ////sqrt      开平方根
            //Console.WriteLine(Math.Sqrt(4));
            ////pi        π    3.141592
            //Console.WriteLine(Math.PI);
            ////round     四舍五入
            ////奇数.5的时候取得是上线
            ////偶数.5的时候取得是下线
            //Console.WriteLine(Math.Round(4.5));
            //Console.ReadLine();

            //DateTime      时间日期类型
            //使用之前应该进行初始化
            //DateTime dt = new DateTime();
            //获取当前时间
            //DateTime dt = DateTime.Now;
            //Console.WriteLine(dt);

            //Console.WriteLine(dt.Month);
            //            获取年  dt.Year
            //获取月  dt.Month
            //获取日  dt.Day
            //获取小时  dt.Hour
            //获取分  dt.Minute
            //获取秒  dt.Second

            //获取星期几
            //DayOfWeek d = dt.DayOfWeek;
            ////Console.WriteLine(d);
            //string dow =d.ToString();
            //switch(dow)
            //{
            //    case "Monday":
            //        Console.WriteLine("星期一");
            //        break;
            //    case "Tuesday":
            //        Console.WriteLine("星期二");
            //        break;
            //}
           

            //Add()     增加或减少
            //TimeSpan span = new TimeSpan(3, 3, 3, 3);
            //Console.WriteLine(dt.Add(span));

            ////增加多少天
            //Console.WriteLine( dt.AddDays(-7.5));

            //输入两个时间日期，计算出相差多少天（TotalDays）
            //Console.Write("请输入第一个时间日期（****/**/** **:**:**）:");
            //DateTime dt1 = DateTime.Parse(Console.ReadLine());
            //Console.Write("请输入第二个时间日期（****/**/** **:**:**）:");
            //DateTime dt2 = DateTime.Parse(Console.ReadLine());

            //Console.WriteLine((dt2-dt1).TotalDays);

            //高考倒计时
            //QQ情侣
            //Console.Write("请输入你们恋爱开始的时间日期：");
            //DateTime dt1 = DateTime.Parse(Console.ReadLine());
            //DateTime dt2 = DateTime.Now;
            //Console.WriteLine("已经恋爱了{0}天。",Math.Ceiling( (dt2-dt1).TotalDays));

            //Console.ReadLine();

            //try
            //{
            //    Console.Write("请输入一个时间日期：");
            //    DateTime dt = DateTime.Parse(Console.ReadLine());
            //    Console.WriteLine("您输入的时间日期格式正确！");
            //}
            //catch
            //{
            //    Console.WriteLine("您输入的时间日期有误！");
            //}
            //Console.WriteLine("感谢使用！");
            //Console.ReadLine();

   3.随机数类     Random
            //初始化
            //Random ran = new Random();
            ////int a = ran.Next(101);
            //int b = ran.Next(1,37);