Java语言高分悬赏：使用多线程编程技术计算自然底数的值，并且和单线程比较，运行时间分别是多少

Java语言高分悬赏：使用多线程编程技术计算自然底数的值，并且和单线程比较，运行时间分别是多少

package lesson19;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Date;

public class MovieStone
{

public static void main(String[] args)
{
    long begin=new Date().getTime();
    InputStream in=null;
    OutputStream out=null;
    File dir=new File("D:\\export");
    File[] listFiles = dir.listFiles();
    for(int i=0;i<listFiles.length;i++)
    {
        try
        {
            in=new FileInputStream(listFiles[i]);
            out=new FileOutputStream("D:\\新地方\\"+listFiles[i].getName());
            byte[] b=new byte[1024];
            int len=0;
            while((len=in.read(b))!=-1)
            {

            out.write(b,0,len);
            }
        }
        catch (FileNotFoundException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        catch (IOException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        finally
        {
            try
            {
                in.close();
                out.close();
            }
            catch (IOException e)
            {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }



    }
    long end=new Date().getTime();
    System.out.println(end-begin);
}

}