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IndexOf() LastIndexOf() Contains() StartsWith() EndsWith()方法比较

慎壹 2022-08-06 阅读 141

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Diagnostics;

namespace CA100
{
class Program
{
//循环次数:5百万次
const int COUNT = 5000000;
//外围循环次数:5次
const int NUM = 5;
//准确测量运行时间
static Stopwatch sWatch = new Stopwatch();
//每项时间
static long t1, t2;
//记录日志
static StringBuilder sb = new StringBuilder();

static void Main()
{
string src = "C#测试IndexOf()LastIndexOf()Contains()StartsWith()EndsWith()5个方法的效率.";
Console.WriteLine("测试的字符串是:" + src + ",测试次数" + COUNT);
sb.AppendLine("测试的字符串是:" + src + ",测试次数" + COUNT);
string str = "C";
//每项循环测试5次
int i = 0;
Console.WriteLine("\n'C'出现在首位时:\n");
sb.AppendLine("\r\n'C'出现在首位时:\r\n");
for (; i < NUM; i++)
{
Console.WriteLine("当前循环第{0}次\n", i + 1);
sb.AppendLine("当前循环第" + (i + 1) + "次");
t1 += IndexOf(src, str);
t2 += StartsWith(src, str);
Console.WriteLine();
sb.AppendLine();
}
Console.WriteLine("IndexOf总时间:" + t1 + ",平均时间:" + t1 / NUM);
sb.AppendLine("IndexOf总时间:" + t1 + ",平均时间:" + t1 / NUM);
Console.WriteLine("StartsWith总时间:" + t2 + ",平均时间:" + t2 / NUM);
sb.AppendLine("StartsWith总时间:" + t2 + ",平均时间:" + t2 / NUM);
Console.WriteLine();
sb.AppendLine();
t1 = 0;
t2 = 0;

str = "StartsWith";
Console.WriteLine("'StartsWith'出现在中间:\n");
sb.AppendLine("'StartsWith'出现在中间:\r\n");
for (i = 0; i < NUM; i++)
{
Console.WriteLine("当前循环第{0}次\n", i + 1);
sb.AppendLine("当前循环第" + (i + 1) + "次");
t1 += IndexOf(src, str);
t2 += Contains(src, str);
Console.WriteLine();
sb.AppendLine();
}

Console.WriteLine("IndexOf总时间:" + t1 + ",平均时间:" + t1 / NUM);
sb.AppendLine("IndexOf总时间:" + t1 + ",平均时间:" + t1 / NUM);
Console.WriteLine("Contains总时间:" + t2 + ",平均时间:" + t2 / NUM);
sb.AppendLine("Contains总时间:" + t2 + ",平均时间:" + t2 / NUM);
Console.WriteLine();
sb.AppendLine();
t1 = 0;
t2 = 0;

str = ".";
Console.WriteLine("'.'出现在末尾:\n");
sb.AppendLine("'.'出现在末尾:\r\n");
for (i = 0; i < NUM; i++)
{
Console.WriteLine("当前循环第{0}次\n", i + 1);
sb.AppendLine("当前循环第" + (i + 1) + "次");
t1 += LastIndexOf(src, str);
t2 += EndsWith(src, str);
Console.WriteLine();
sb.AppendLine();
}

Console.WriteLine("LastIndexOf总时间:" + t1 + ",平均时间:" + t1 / NUM);
sb.AppendLine("LastIndexOf总时间:" + t1 + ",平均时间:" + t1 / NUM);
Console.WriteLine("EndsWith总时间:" + t2 + ",平均时间:" + t2 / NUM);
sb.AppendLine("EndsWith总时间:" + t2 + ",平均时间:" + t2 / NUM);
Console.WriteLine();
sb.AppendLine();

Console.WriteLine("测试结束!");
sb.AppendLine("测试结束!");

File.AppendAllText(@"d:\results.txt", sb.ToString());
Console.ReadLine();
}

static long IndexOf(string src, string str)
{
sWatch.Reset();
sWatch.Start();
for (int i = 0; i < COUNT; i++)
{
src.IndexOf(str);
}
sWatch.Stop();

Console.WriteLine("IndexOf花费: " + sWatch.ElapsedMilliseconds + "ms");
sb.AppendLine("IndexOf花费: " + sWatch.ElapsedMilliseconds + "ms");
return sWatch.ElapsedMilliseconds;
}

static long LastIndexOf(string src, string str)
{
sWatch.Reset();
sWatch.Start();
for (int i = 0; i < COUNT; i++)
{
src.LastIndexOf(str);
}
sWatch.Stop();

Console.WriteLine("LastIndexOf花费: " + sWatch.ElapsedMilliseconds + "ms");
sb.AppendLine("LastIndexOf花费: " + sWatch.ElapsedMilliseconds + "ms");
return sWatch.ElapsedMilliseconds;
}

static long StartsWith(string src, string str)
{
sWatch.Reset();
sWatch.Start();
for (int i = 0; i < COUNT; i++)
{
src.StartsWith(str);
}
sWatch.Stop();

Console.WriteLine("StartsWith花费: " + sWatch.ElapsedMilliseconds + "ms");
sb.AppendLine("StartsWith花费: " + sWatch.ElapsedMilliseconds + "ms");
return sWatch.ElapsedMilliseconds;
}

static long EndsWith(string src, string str)
{
sWatch.Reset();
sWatch.Start();
for (int i = 0; i < COUNT; i++)
{
src.EndsWith(str);
}
sWatch.Stop();

Console.WriteLine("EndsWith花费: " + sWatch.ElapsedMilliseconds + "ms");
sb.AppendLine("EndsWith花费: " + sWatch.ElapsedMilliseconds + "ms");
return sWatch.ElapsedMilliseconds;
}

static long Contains(string src, string str)
{
sWatch.Reset();
sWatch.Start();
for (int i = 0; i < COUNT; i++)
{
src.Contains(str);
}
sWatch.Stop();

Console.WriteLine("Contains花费: " + sWatch.ElapsedMilliseconds + "ms");
sb.AppendLine("Contains花费: " + sWatch.ElapsedMilliseconds + "ms");
return sWatch.ElapsedMilliseconds;
}
}
}

 

针对三种情况

1.判断以字符串开头

IndexOf和StartsWith

2.判断是否包含字符串

IndexOf和Contains

3.判断以字符串结尾

LastIndexOf和EndsWith

 

测试以某字符串为开头,以使用IndexOf为最佳,有时,StartsWith也会比IndexOf快,几率较低。

测试包含字符串,以Contains最佳。

测试以某字符串结尾,虽然LastIndexOf速度略快,但是不好判定,还是采用EndsWith为最佳。



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