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From: Wojtek <nowhere@a.com>
Newsgroups: comp.lang.java.programmer
Subject: Re: The first 10 files
Date: Thu, 14 Mar 2013 03:07:10 -0700
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Knute Johnson wrote :
>
> 300003 files in the directory, almost 1.7GB of files, Windows XP, Java 7 and 
> it takes 16 ms to run.  Somebody else should try this out on their computer 
> to see if it works as fast.

Ok, I'm back :-)

I am using WinXP and Java 7, and the directory holds 30,001 32K files,
920MBytes

The Code:
----------------------------------------------------
package tester;

import java.io.File;
import java.io.IOException;
import java.nio.file.DirectoryStream;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;

public class NewsGroup
{
  public static void main( String[] args ) throws IOException
  {
    int maxFiles = 10;

    System.out.println( "Large File Number Tester" );

    if (args[0].equals( "nio" ))
      nioRun( "C:\\apps\\test", maxFiles );

    else if (args[0].equals( "io" ))
      ioRun( "C:\\apps\\test", maxFiles );

    else
      System.out.println( "NewsGroup io|nio" );

  }

  private static void ioRun( String filePath, int maxFiles ) throws 
IOException
  {
    int i = 1;

    System.out.println( "IO run" );
    long start = System.currentTimeMillis();

    File folder = new File( filePath );
    File[] listOfFiles = folder.listFiles();

    for (File file : listOfFiles)
    {
      System.out.println( "" + i + ": " + file.getName() );

      if (++i > maxFiles)
        break;
    }

    long stop = System.currentTimeMillis();

    System.out.println( "Elapsed: " + (stop - start) + " ms" );
  }

  private static void nioRun( String filePath, int maxFiles ) throws 
IOException
  {
    int i = 1;

    System.out.println( "NIO run" );
    long start = System.currentTimeMillis();

    Path dir = FileSystems.getDefault().getPath( filePath );
    DirectoryStream<Path> stream = Files.newDirectoryStream( dir );

    for (Path path : stream)
    {
      System.out.println( "" + i + ": " + path.getFileName() );

      if (++i > maxFiles)
        break;
    }

    long stop = System.currentTimeMillis();

    System.out.println( "Elapsed: " + (stop - start) + " ms" );
  }
}
----------------------------------------------------

A batch file to run it:
----------------------------------------------------
@echo off
java -jar NewsGroup.jar %1
----------------------------------------------------

And the results:
----------------------------------------------------
C:\apps>run io
Large File Number Tester
IO run
1: F_000000.jpg
2: F_000001.jpg
3: F_000002.jpg
4: F_000003.jpg
5: F_000004.jpg
6: F_000005.jpg
7: F_000006.jpg
8: F_000007.jpg
9: F_000008.jpg
10: F_000009.jpg
Elapsed: 156 ms

C:\apps>run io
Large File Number Tester
IO run
1: F_000000.jpg
2: F_000001.jpg
3: F_000002.jpg
4: F_000003.jpg
5: F_000004.jpg
6: F_000005.jpg
7: F_000006.jpg
8: F_000007.jpg
9: F_000008.jpg
10: F_000009.jpg
Elapsed: 140 ms

C:\apps>run io
Large File Number Tester
IO run
1: F_000000.jpg
2: F_000001.jpg
3: F_000002.jpg
4: F_000003.jpg
5: F_000004.jpg
6: F_000005.jpg
7: F_000006.jpg
8: F_000007.jpg
9: F_000008.jpg
10: F_000009.jpg
Elapsed: 156 ms

C:\apps>run nio
Large File Number Tester
NIO run
1: F_000000.jpg
2: F_000001.jpg
3: F_000002.jpg
4: F_000003.jpg
5: F_000004.jpg
6: F_000005.jpg
7: F_000006.jpg
8: F_000007.jpg
9: F_000008.jpg
10: F_000009.jpg
Elapsed: 219 ms

C:\apps>run nio
Large File Number Tester
NIO run
1: F_000000.jpg
2: F_000001.jpg
3: F_000002.jpg
4: F_000003.jpg
5: F_000004.jpg
6: F_000005.jpg
7: F_000006.jpg
8: F_000007.jpg
9: F_000008.jpg
10: F_000009.jpg
Elapsed: 31 ms

C:\apps>run nio
Large File Number Tester
NIO run
1: F_000000.jpg
2: F_000001.jpg
3: F_000002.jpg
4: F_000003.jpg
5: F_000004.jpg
6: F_000005.jpg
7: F_000006.jpg
8: F_000007.jpg
9: F_000008.jpg
10: F_000009.jpg
Elapsed: 31 ms

C:\apps>run nio
Large File Number Tester
NIO run
1: F_000000.jpg
2: F_000001.jpg
3: F_000002.jpg
4: F_000003.jpg
5: F_000004.jpg
6: F_000005.jpg
7: F_000006.jpg
8: F_000007.jpg
9: F_000008.jpg
10: F_000009.jpg
Elapsed: 78 ms

C:\apps>
----------------------------------------------------

So NIO is about 4-5 times faster than IO. The first NIO run looks like 
an anomoly, might be some JRE loading happening.

All the runs produce different timings, might be a Windows caching 
effect. However the NIO is consistently much faster overall.

-- 
Wojtek :-)