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From: Knute Johnson <nospam@knutejohnson.com>
Newsgroups: comp.lang.java.programmer
Subject: Re: The first 10 files
Date: Sat, 26 Jan 2013 18:37:09 -0800
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On 1/26/2013 1:14 AM, Wojtek wrote:
> Using:
>
> int max = 10;
> int count = 0;
>
> for (File thisFile : aDir.listFiles())
> {
>   doSomething(thisFile);
>
>   if ( ++count >= max )
>     break;
> }
>
> gives me the first ten files in aDir. But if aDir contains 30K files,
> then the listFiles() will run for a long time as it builds an array for
> the 30K files.
>
> Is there a way to have Java only get the first "max" files?
>

import java.io.*;
import java.nio.*;
import java.nio.file.*;

public class FileSystemsTest {
     public static void main(String[] args) throws IOException {
         long start = System.currentTimeMillis();
         Path dir = FileSystems.getDefault().getPath(".");
         int i=10;
         DirectoryStream<Path> stream = Files.newDirectoryStream(dir);
         for (Path path : stream) {
             System.out.println(path.getFileName());
             if (--i <= 0)
                 break;
         }
         long stop = System.currentTimeMillis();
         System.out.println(stop - start);
     }
}

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.

.
.
.
01/26/2013  05:46 PM            58,890 9998.txt
01/26/2013  05:46 PM            58,890 9999.txt
01/26/2013  06:31 PM             1,316 FileSystemsTest.class
01/26/2013  06:29 PM               636 FileSystemsTest.java
01/26/2013  05:44 PM               650 MakeFiles.java
            30003 File(s)  1,766,702,602 bytes
                2 Dir(s)  49,387,085,824 bytes free

C:\Documents and Settings\Knute Johnson\bigdirectory>java FileSystemsTest
0.txt
1.txt
10.txt
100.txt
1000.txt
10000.txt
10001.txt
10002.txt
10003.txt
10004.txt
16

C:\Documents and Settings\Knute Johnson\bigdirectory>


-- 

Knute Johnson