using System;

using System.Diagnostics;

​

class Program

{

    static void Main()

    {

        string testString = "apple";

        int iterations = 1; // 一亿次迭代

​

        // 测试 str.StartsWith("a")

        Stopwatch stopwatch1 = new Stopwatch();

        stopwatch1.Start();

        for (int i = 0; i < iterations; i++)

        {

            bool startsWithA1 = testString.StartsWith("a");

        }

        stopwatch1.Stop();

        Console.WriteLine($"str.StartsWith(\"a\") 执行时间: {stopwatch1.Elapsed.TotalMilliseconds} 毫秒");

​

        // 测试 str[0] == 'a'

        Stopwatch stopwatch2 = new Stopwatch();

        stopwatch2.Start();

        for (int i = 0; i < iterations; i++)

        {

            bool startsWithA2 = testString!=null&&testString.Length>0&&testString[0] == 'a';

        }

        stopwatch2.Stop();

        Console.WriteLine($"str[0] == 'a' 执行时间: {stopwatch2.Elapsed.TotalMilliseconds} 毫秒");

    }

}