字符串中判断存在的几种模式和效率(string.contains、string.IndexOf、Regex.Match)-白红宇

字符串中判断存在的几种模式和效率(string.contains、string.IndexOf、Regex.Match)

阅读量：5122 次

发布时间：2019-06-13

本文共 5349 字，大约阅读时间需要 17 分钟。

通常情况下，我们判断一个字符串中是否存在某值常常会用string.contains，其实判断一个字符串中存在某值的方法有很多种，最常用的就是前述所说的string.contains，相对来说比较常用的还有string.IndexOf和Regex.Match。直接上代码，后面在说些什么吧，通常情况下功能的实现最重要，作者的话，只对有心者有效。

using System;using System.Collections.Generic;using System.Linq; using System.Text; using System.Text.RegularExpressions; namespace ExistsInString { class Program { static void Main(string[] args) { string str0 = "|456|"; string str1 = "|444|"; string str2 = "|111|222|333|444|555|666|777|888|999|000|"; //------------------------------------------ //String.Contains方法 if (str2.Contains(str0)) Console.WriteLine("String.Contains->true"); else Console.WriteLine("String.Contains->false"); if (str2.Contains(str1)) Console.WriteLine("String.Contains->true"); else Console.WriteLine("String.Contains->false"); //------------------------------------------ //String.IndexOf方法 int val1 = str2.IndexOf(str0);//不存在返回-1 Console.WriteLine("String.IndexOf(no exists)->" + val1); int val2 = str2.IndexOf(str1);//存在返回str1首字符所在str2中的位置(>=0) Console.WriteLine("String.IndexOf(exists)->" + val2); //------------------------------------------ //正则匹配方法 if (Regex.Match(str2, "[|]456[|]").Success) Console.WriteLine("Regex.Match(no exists)->true"); else Console.WriteLine("Regex.Match(no exists)->false"); if (Regex.Match(str2, "[|]444[|]").Success) Console.WriteLine("Regex.Match(exists)->true"); else Console.WriteLine("Regex.Match(exists)->false"); Console.ReadKey(); /* *如果上述三种方式都处理大量数据，效率如何呢？ *以下循环六组数据说明 */ int loopCount = (int)10e6; DateTime lasttime = DateTime.Now; DateTime nowtime = DateTime.Now; for (int loop = 1; loop < 7; loop++) { Console.WriteLine("\r\nloop " + loop + " >>>>>>>"); //------------------------------------------ //String.Contains方法 //no exists lasttime = DateTime.Now; for (int i = 0; i < loopCount; i++) if (str2.Contains(str0)) { }; nowtime = DateTime.Now; TimeSpan tsStrConNoExists = nowtime - lasttime; //exists lasttime = DateTime.Now; for (int i = 0; i < loopCount; i++) if (str2.Contains(str1)) { }; nowtime = DateTime.Now; TimeSpan tsStrConExists = nowtime - lasttime; //------------------------------------------ //String.IndexOf方法 //no exists lasttime = DateTime.Now; for (int i = 0; i < loopCount; i++) if (str2.IndexOf(str0) >= 0) { };//上述已经提到不存在返回-1，存在返回一个非负整数，这里为什么不用 == -1 ，而是用了 >= 0 ，这是一个值得深思的问题？ nowtime = DateTime.Now; TimeSpan tsStrIndNoExists = nowtime - lasttime; //exists lasttime = DateTime.Now; for (int i = 0; i < loopCount; i++) if (str2.IndexOf(str1) >= 0) { }; nowtime = DateTime.Now; TimeSpan tsStrIndExists = nowtime - lasttime; //------------------------------------------ //Regex.Match方法 //no exists Regex Reg0 = new Regex("[|]456[|]"); lasttime = DateTime.Now; for (int i = 0; i < loopCount; i++) if (Reg0.Match(str2).Success) { }; nowtime = DateTime.Now; TimeSpan tsStrRegNoExists = nowtime - lasttime; //exists Regex Reg1 = new Regex("[|]444[|]"); lasttime = DateTime.Now; for (int i = 0; i < loopCount; i++) if (Reg1.Match(str2).Success) { }; nowtime = DateTime.Now; TimeSpan tsStrRegExists = nowtime - lasttime; Console.WriteLine("no exists >>>"); Console.WriteLine("tsStrConNoExists = " + tsStrConNoExists.Milliseconds); Console.WriteLine("tsStrIndNoExists = " + tsStrIndNoExists.Milliseconds); Console.WriteLine("tsStrRegNoExists = " + tsStrRegNoExists.Milliseconds); Console.WriteLine("exists >>>"); Console.WriteLine("tsStrConExists = " + tsStrConExists.Milliseconds); Console.WriteLine("tsStrIndExists = " + tsStrIndExists.Milliseconds); Console.WriteLine("tsStrRegExists = " + tsStrRegExists.Milliseconds); } Console.ReadKey(); } } }

输入结果：

String.Contains->false

String.Contains->true

String.IndexOf(no exists)->-1

String.IndexOf(exists)->12

Regex.Match(no exists)->false

Regex.Match(exists)->true

loop 1 >>>>>>>

no exists >>>

tsStrConNoExists = 796

tsStrIndNoExists = 687

tsStrRegNoExists = 171