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C# 判断字符为空的6种方法的效率实测对比

2016-05-04 11:47 1071 查看

C#中提供了相当丰富的方法或属性来判断一个字符是否为空，常用的方法有以下6种

1. strTest== ""

2. strTest.Equals("")

3. strTest== string.Empty

4. strTest.Equals(string.Empty)

5. strTest.Length == 0

6. string.IsNullOrEmpty(strTest)

为了对以上6种方法的效率，有个直观的感受，我特意编写了以下的测试代码：

using System;

namespace StrTest
{
class Program
{
//定义3个字符串 以便测试在多种情况下 下面6种判断方法的速度
public static string strTest01 = "";
public static string strTest02 = string.Empty;
public static string strTest03 = "0123456789";

public static DateTime start, end; //定义开始时间 和 结束时间
public static TimeSpan ts;    //定义两个时间的间隔

//**********************对strTest使用6种测试方法*****************************
public static void Test(string strTest)
{
//string == ""
start = DateTime.Now;
for (int counter = 0; counter <= 100000000; counter++)
{
if (strTest == "")
{
}
}
end = DateTime.Now;
ts = end - start;
Console.WriteLine("string == /"/" 时间消耗为 " + ts.TotalSeconds + " 秒");

//string.Equals("")
start = DateTime.Now;
for (int counter = 0; counter <= 100000000; counter++)
{
if (strTest.Equals(""))
{
}
}
end = DateTime.Now;
ts = end - start;
Console.WriteLine("string.Equals(/"/") 时间消耗为 " + ts.TotalSeconds + " 秒");

//string == stirng.Empty
start = DateTime.Now;
for (int counter = 0; counter <= 100000000; counter++)
{
if (strTest == string.Empty)
{
}
}
end = DateTime.Now;
ts = end - start;
Console.WriteLine("string == string.Empty 时间消耗为 " + ts.TotalSeconds + " 秒");

//string.Equals(string.Empty)
start = DateTime.Now;
for (int counter = 0; counter <= 100000000; counter++)
{
if (strTest.Equals(string.Empty))
{
}
}
end = DateTime.Now;
ts = end - start;
Console.WriteLine("string.Equals(string.Empty) 时间消耗为 " + ts.TotalSeconds + " 秒");

//string.Length == 0
start = DateTime.Now;
for (int counter = 0; counter <= 100000000; counter++)
{
if (strTest.Length == 0)
{
}
}
end = DateTime.Now;
ts = end - start;
Console.WriteLine("string.Length == 0 时间消耗为 " + ts.TotalSeconds + " 秒");

//string.IsNullOrEmpty(string)
start = DateTime.Now;
for (int counter = 0; counter <= 100000000; counter++)
{
if (string.IsNullOrEmpty(strTest))
{
}
}
end = DateTime.Now;
ts = end - start;
Console.WriteLine("string.IsNullOrEmpty(string) 时间消耗为 " + ts.TotalSeconds + " 秒" + "/n");
}

static void Main(string[] args)
{
Console.WriteLine("=======================================");
Console.WriteLine("strTest = /"/" 的5种测试结果");
Console.WriteLine("=======================================");

Test(strTest01);

Console.WriteLine("=======================================");
Console.WriteLine("strTest = string.Emtpy 的5种测试结果");
Console.WriteLine("=======================================");

Test(strTest02);

Console.WriteLine("=======================================");
Console.WriteLine("strTest = /"0123456789/" 的5种测试结果");
Console.WriteLine("=======================================");

Test(strTest03);

Console.ReadLine();  //等待键盘的输入 作用:使屏幕暂停在此处
}
}
}

我把能关的软件都关闭掉了尽可能的屏蔽掉系统影响并且让6种方法都运行了1亿次

第一次的截图：