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

Posted 2020-08-16 石

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。