using System;using System.Collections.Generic;using System.Linq;using System.Text;namespace StringFormatEfficiency{ class PRogram { static void Main(string[] args) { string format = "my {0} is {1}"; string name = "name"; string zhangyaolin = "zhangyaolin"; string my = "my "; string iss = " is "; DateTime start = new DateTime(); DateTime end = new DateTime(); string aa = null; int maxcount = 10e6; for (int ii = 0; ii < 10; ii++) { start = DateTime.Now; for (int i = 0; i < maxcount; i++) { aa = string.Format(format, name, zhangyaolin); } end = DateTime.Now; TimeSpan ts1 = end - start; Console.WriteLine(ts1.Milliseconds.ToString()); //------------------------- start = DateTime.Now; for (int i = 0; i < maxcount; i++) { aa = string.Concat(my, name, iss, zhangyaolin); } end = DateTime.Now; TimeSpan ts2 = end - start; Console.WriteLine(ts2.Milliseconds.ToString()); //-------------------------- start = DateTime.Now; for (int i = 0; i < maxcount; i++) { aa = my + name + iss + zhangyaolin; } end = DateTime.Now; TimeSpan ts3 = end - start; Console.WriteLine(ts3.Milliseconds.ToString()); Console.WriteLine("time1(format) : time2(connect) : time3(Operator) = {0} : {1} : 1", (1.0 * ts1.Milliseconds / ts3.Milliseconds).ToString(“F3”), (1.0 * ts2.Milliseconds / ts3.Milliseconds).ToString(“F3”)); Console.WriteLine(); } } }}
测试结果:
531109125time1(format) : time2(connect) : time3(operator) = 4.248 : 0.872 : 1531109109time1(format) : time2(connect) : time3(operator) = 4.872 : 1.000 : 1515125109time1(format) : time2(connect) : time3(operator) = 4.725 : 1.147 : 1531109109time1(format) : time2(connect) : time3(operator) = 4.872 : 1.000 : 1531125109time1(format) : time2(connect) : time3(operator) = 4.872 : 1.147 : 1531109109time1(format) : time2(connect) : time3(operator) = 4.872 : 1.000 : 1531109109time1(format) : time2(connect) : time3(operator) = 4.872 : 1.000 : 1531109109time1(format) : time2(connect) : time3(operator) = 4.872 : 1.000 : 1531125109time1(format) : time2(connect) : time3(operator) = 4.872 : 1.147 : 1531109125time1(format) : time2(connect) : time3(operator) = 4.248 : 0.872 : 1原因: string.format和string.connect都执行了新地址分配和入栈操作,不过string.format会对每个入栈字符检查判断,当有{/d+}这种替换字符出现时,会将{/d+}对应的字符序列入栈;而string.connect只做入栈,不做入栈字符的检查和判断。入栈操作完成时,做出栈操作,将栈内字符有序的放入堆里。理论上来说,string.format操作的字符串越长,效率越低。注:/d+表示一个数字,如string format = "my {0} is {1}";中的0和1新闻热点
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