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Re: The first 10 files

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Arved Sandstrom <asandstrom2@eastlink.ca> writes:

> On 01/26/2013 09:42 PM, Eric Sosman wrote:
>> On 1/26/2013 6:21 PM, Peter Duniho wrote:
>>> On Sat, 26 Jan 2013 17:06:07 -0500, Eric Sosman wrote:
>>>
>>>> On 1/26/2013 4:15 PM, Robert Klemme wrote:
>>>>> On 26.01.2013 19:26, Arne Vajhøj wrote:
>>>>>
>>>>>> But I am a bit skeptical about whether a String[] with 30K elements
>>>>>> is really the bottleneck.
>>>>>>
>>>>>> If the real bottleneck is the OS calls to get next file, then
>>>>>> a filter like this will not help.
>>>>>
>>>>> Why?
>>>>
>>>>       Because the listFiles() method will fetch the information
>>>> for all 30K files from the O/S, will construct 30K File objects
>>>> to represent them, and will submit all 30K File objects to the
>>>> FileFilter, one by one.  The FileFilter will (very quickly)
>>>> reject 29.99K of the 30K Files, but ...
>>>
>>> Will it?
>>
>>      Necessarily.  As far as listFiles() knows, the FileFilter
>> might accept the very last File object given to it.  Therefore,
>> listFiles() cannot fail to present that very last File -- and
>> every other File -- for inspection.
> [ SNIP ]
>
> I'd have to agree. A simple test shows this to be the case, but your
> reasoning precludes having to run such a test in the first place.
>
> My code "gets' the first N files from listFiles(), for some definition
> of "first", but it certainly doesn't only get N files from the OS.
>
> Based on Wojtek's later post, I'd be examining the entire problem in
> more detail before arriving at a decent solution. I don't think most
> of the problem pertaining to offering reasonable batches of files to a
> Java program for processing is something that I'd address in Java
> anyway.

There's also the problem of starvation, since we have no guarantees
concerning the order of entries in the directory.

-- 
Jim Janney

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The first 10 files Wojtek <nowhere@a.com> - 2013-01-26 01:14 -0800
  Re: The first 10 files Roedy Green <see_website@mindprod.com.invalid> - 2013-01-26 02:44 -0800
    Re: The first 10 files Lew <lewbloch@gmail.com> - 2013-01-26 10:20 -0800
  Re: The first 10 files "John B. Matthews" <nospam@nospam.invalid> - 2013-01-26 06:31 -0500
    Re: The first 10 files Wojtek <nowhere@a.com> - 2013-01-26 15:42 -0800
      Re: The first 10 files Jim Janney <jjanney@shell.xmission.com> - 2013-01-26 17:13 -0700
      Re: The first 10 files Arne Vajhøj <arne@vajhoej.dk> - 2013-01-26 21:21 -0500
      Re: The first 10 files "John B. Matthews" <nospam@nospam.invalid> - 2013-01-26 22:05 -0500
  Re: The first 10 files Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-01-26 08:24 -0400
    Re: The first 10 files Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-01-26 08:25 -0400
    Re: The first 10 files Arne Vajhøj <arne@vajhoej.dk> - 2013-01-26 13:26 -0500
      Re: The first 10 files Robert Klemme <shortcutter@googlemail.com> - 2013-01-26 22:15 +0100
        Re: The first 10 files Arne Vajhøj <arne@vajhoej.dk> - 2013-01-26 16:25 -0500
        Re: The first 10 files Eric Sosman <esosman@comcast-dot-net.invalid> - 2013-01-26 17:06 -0500
          Re: The first 10 files Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2013-01-26 15:21 -0800
            Re: The first 10 files Eric Sosman <esosman@comcast-dot-net.invalid> - 2013-01-26 20:42 -0500
              Re: The first 10 files Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2013-01-26 17:56 -0800
                Re: The first 10 files Arne Vajhøj <arne@vajhoej.dk> - 2013-01-26 21:29 -0500
                Re: The first 10 files Eric Sosman <esosman@comcast-dot-net.invalid> - 2013-01-26 21:56 -0500
                Re: The first 10 files Jim Janney <jjanney@shell.xmission.com> - 2013-01-26 20:51 -0700
                Re: The first 10 files Jim Janney <jjanney@shell.xmission.com> - 2013-01-26 20:47 -0700
              Re: The first 10 files Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-01-26 22:02 -0400
                Re: The first 10 files Arne Vajhøj <arne@vajhoej.dk> - 2013-01-26 21:35 -0500
                Re: The first 10 files Arne Vajhøj <arne@vajhoej.dk> - 2013-01-26 21:43 -0500
                Re: The first 10 files Robert Klemme <shortcutter@googlemail.com> - 2013-01-27 13:55 +0100
                Re: The first 10 files Arne Vajhøj <arne@vajhoej.dk> - 2013-02-24 17:50 -0500
                Re: The first 10 files Robert Klemme <shortcutter@googlemail.com> - 2013-02-25 21:53 +0100
                Re: The first 10 files Jim Janney <jjanney@shell.xmission.com> - 2013-01-26 20:57 -0700
                Re: The first 10 files Wojtek <nowhere@a.com> - 2013-01-26 21:20 -0800
                Re: The first 10 files Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-01-27 07:23 -0400
                Re: The first 10 files Arne Vajhøj <arne@vajhoej.dk> - 2013-01-27 20:36 -0500
                Re: The first 10 files Wojtek <nowhere@a.com> - 2013-01-28 16:28 -0800
            Re: The first 10 files Arne Vajhøj <arne@vajhoej.dk> - 2013-01-26 21:23 -0500
            Re: The first 10 files Roedy Green <see_website@mindprod.com.invalid> - 2013-01-26 19:09 -0800
  Re: The first 10 files Jim Janney <jjanney@shell.xmission.com> - 2013-01-26 16:00 -0700
  Re: The first 10 files Knute Johnson <nospam@knutejohnson.com> - 2013-01-26 18:37 -0800
    Re: The first 10 files Wojtek <nowhere@a.com> - 2013-03-14 03:07 -0700
      Re: The first 10 files lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-03-14 12:49 +0000
      Re: The first 10 files Robert Klemme <shortcutter@googlemail.com> - 2013-03-15 11:38 +0100
        Re: The first 10 files Wojtek <nowhere@a.com> - 2013-03-15 10:31 -0700

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