五、C#—字符串

一、字符串

1.1 字符类型

何时使用字符

遇到字符 '\' 时出现的错误

1.2 转义字符

转义字符使用技巧

1.3 字符串的声明及赋值

1.3.1 c# 中的字符串

1.3.2 声明字符串

1.3.3 使用字符串

1.3.4 字符串的初始化

1.3.4.1 引用字符串常量之初始化

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace ConsoleApp6
{class Program{static void Main(string[] args){String str = "时间就是金钱";Console.WriteLine(str);Console.ReadLine();}}
}

1.3.4.2 利用字符数组初始化

1.3.4.3 提取数组中的一部分进行初始化

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace ConsoleApp6
{class Program{static void Main(string[] args){char[] array = { '时','间','就','是','金','钱'};string str = new string(array);string str2 = new string(array,4,2);Console.WriteLine(str);Console.WriteLine(str2);Console.ReadLine();}}
}

1.3.5 空字符串与空引用的区别

1.3.6 字符串的拼接

判断用户名是否存在

1.3.7 比较字符串的其它方法

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace ConsoleApp6
{class Program{static void Main(string[] args){string str ="mr1";string str2 = "mr12";Console.WriteLine(string.Compare(str,str2));Console.ReadLine();}}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace ConsoleApp6
{class Program{static void Main(string[] args){string str ="mr1";string str2 = "mr12";Console.WriteLine(str.CompareTo(str2));Console.ReadLine();}}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace ConsoleApp6
{class Program{static void Main(string[] args){string str ="mr1";string str2 = "mr12";Console.WriteLine(str.Equals(str2));Console.ReadLine();}}
}

1.4 格式化字符串

1.4.1 标准数值格式规范

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace ConsoleApp6
{class Program{static void Main(string[] args){Console.WriteLine("货币形式:{0:C}",365);Console.WriteLine("科学计数法:{0:E}",12);Console.WriteLine("货币形式:{0:N}",36534);Console.WriteLine("Π取两位小数:{0:F2}",Math.PI);Console.WriteLine("16进制显示:{0:X4}",36);Console.WriteLine("百分比显示:{0:P}",0.99);Console.ReadLine();}}
}

1.4.1 标准日期时间格式规范

1.4.2 格式化的另外一种方法

1.5 截取字符串

从身份证中获取出生日期

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace ConsoleApp7
{class Program{static void Main(string[] args){string fileName = "glorysoft.com";string file = fileName.Substring(0, fileName.IndexOf('.'));string fileT = fileName.Substring(fileName.IndexOf('.'));Console.WriteLine(file);Console.WriteLine(fileT);Console.ReadLine();}}
}

索引或者长度超出字符串范围得错误

1.6 分割字符串

限定分割次数

限定分割次数得执行效果

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace ConsoleApp7
{class Program{static void Main(string[] args){string fileName = "glorysoft.com.com.com";string[] array = fileName.Split(new char[] { '.' },2);for (int i = 0; i < array.Length; i++) {Console.WriteLine(array[i]);}Console.ReadLine();}}
}

1.7 插入字符串

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace ConsoleApp8
{class Program{static void Main(string[] args){string old = "you are a pig";Console.WriteLine(old);string newOld = old.Insert(8, "to");Console.WriteLine(newOld);Console.ReadLine();}}
}

1.8 删除字符串

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace ConsoleApp8
{class Program{static void Main(string[] args){string old = "you are a pig";Console.WriteLine(old);string newOld = old.Remove(4);string newOld2 = old.Remove(4,7);Console.WriteLine(newOld);Console.WriteLine(newOld2);Console.ReadLine();}}
}

1.9 复制字符串

复制字符串的一部分

1.10 替换字符串

替换字符串中的字符

替换字符串中的子字符串

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace ConsoleApp8
{class Program{static void Main(string[] args){string str = "馒头一文一个";Console.WriteLine(str);string str2 = str.Replace("一", "壹");string str3 = str.Replace("馒头","馍馍");Console.WriteLine(str2);Console.WriteLine(str3);Console.ReadLine();}}
}

替换字符串需要注意的事项

1.11 可变字符串类

1.11.1 string创建的字符串是不可变的

1.11.2 可变字符串类 StringBuilder

定义：

1.11.3 StringBuilder 类常用的方法

1.11.4 StringBuilder 类的使用

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace ConsoleApp8
{class Program{static void Main(string[] args){StringBuilder sb = new StringBuilder("(),(),(),4, 6, 7、8)");Console.WriteLine(sb);sb.Remove(0, 9);sb.Insert(0,"(门前大桥下)，（游过一群鸭），（快来快来数一数）,");Console.WriteLine(sb);Console.ReadLine();}}
}

1.11.5 字符串与可变字符串的区别

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace ConsoleApp8
{class Program{static void Main(string[] args){long start = DateTime.Now.Millisecond;string a = "";for (int i = 0; i <= 10000; i++) {a += i;}long end = DateTime.Now.Millisecond;Console.WriteLine(end - start);StringBuilder sb = new StringBuilder();long start1 = DateTime.Now.Millisecond;for (int j=0; j < 10000;j++) {sb.Append(j);}long end2 = DateTime.Now.Millisecond;Console.WriteLine(end2-start1);Console.ReadLine();}}
}