为什么StringBuilder与连接相比较慢？
StringBuilder旨在避免额外的对象创建,但是为什么会影响性能？
StringBuilder旨在避免额外的对象创建,但是为什么会影响性能？
static void Main(string[] args)
{
int max = 1000000;
for (int times = 0; times < 5; times++)
{
Console.WriteLine("\ntime: {0}",(times+1).ToString());
Stopwatch sw = Stopwatch.StartNew();
for (int i = 0; i < max; i++)
{
string msg = "Your total is ";
msg += "$500 ";
msg += DateTime.Now;
}
sw.Stop();
Console.WriteLine("String +\t: {0}ms",((int)sw.ElapsedMilliseconds).ToString().PadLeft(6));
sw = Stopwatch.StartNew();
for (int j = 0; j < max; j++)
{
StringBuilder msg = new StringBuilder();
msg.Append("Your total is ");
msg.Append("$500 ");
msg.Append(DateTime.Now);
}
sw.Stop();
Console.WriteLine("StringBuilder\t: {0}ms",((int)sw.ElapsedMilliseconds).ToString().PadLeft(6));
}
Console.Read();
}
编辑：根据建议移出范围变量：
解决方法
更改,以使StringBuilder不被实例化,而不是.Clear()它：
time: 1 String + : 3348ms StringBuilder : 3151ms time: 2 String + : 3346ms StringBuilder : 3050ms
等等
请注意,这仍然测试完全相同的功能,但尝试重新使用资源一点更聪明.
代码：(也住在http://ideone.com/YuaqY)
using System;
using System.Text;
using System.Diagnostics;
public class Program
{
static void Main(string[] args)
{
int max = 1000000;
for (int times = 0; times < 5; times++)
{
{
Console.WriteLine("\ntime: {0}",(times+1).ToString());
Stopwatch sw = Stopwatch.StartNew();
for (int i = 0; i < max; i++)
{
string msg = "Your total is ";
msg += "$500 ";
msg += DateTime.Now;
}
sw.Stop();
Console.WriteLine("String +\t: {0}ms",((int)sw.ElapsedMilliseconds).ToString().PadLeft(6));
}
{
Stopwatch sw = Stopwatch.StartNew();
StringBuilder msg = new StringBuilder();
for (int j = 0; j < max; j++)
{
msg.Clear();
msg.Append("Your total is ");
msg.Append("$500 ");
msg.Append(DateTime.Now);
}
sw.Stop();
Console.WriteLine("StringBuilder\t: {0}ms",((int)sw.ElapsedMilliseconds).ToString().PadLeft(6));
}
}
Console.Read();
}
}
