Java equivalent for MFC findnextfile

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jaja - 07 Aug 2007 08:18 GMT

Hello,
How can I iterate the files inside a directory, like FindNextFile in
Win32.
I don't want to use File.list() which returns me a list of all files.
Thanks.

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Andrew Thompson - 07 Aug 2007 09:01 GMT

...

> How can I iterate the files inside a directory, like FindNextFile in
>Win32.

File.list() or File.listFiles() should provide a list you can iterate..

> I don't want to use File.list() which returns me a list of all files.

You poor thing. Have you considered hiring someone to
code this for you? I am guessing it will save you a lot of
stress.

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Andrew Thompson
http://www.athompson.info/andrew/

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Thomas Fritsch - 07 Aug 2007 10:29 GMT

> How can I iterate the files inside a directory, like FindNextFile in
> Win32.
> I don't want to use File.list() which returns me a list of all files.

Why not?

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Thomas

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jaja - 07 Aug 2007 12:24 GMT

On Aug 7, 12:29 pm, Thomas Fritsch <i.dont.like.s...@invalid.com>
wrote:

> > How can I iterate the files inside a directory, like FindNextFile in
> > Win32.
[quoted text clipped - 4 lines]
> --
> Thomas

Because in case of a huge number of files, the list is very large and
memory consuming.
Do you know a way that I can iterate the files and get it one by one?
Thanks.

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Andrew Thompson - 07 Aug 2007 12:51 GMT

>On Aug 7, 12:29 pm, Thomas Fritsch <i.dont.like.s...@invalid.com>
>wrote:
>> > How can I iterate the files inside a directory, like FindNextFile in
>> > Win32.

(T.F.)

>> Why not?

>Because in case of a huge number of files, the list is very large and
>memory consuming.

Over optimisation.

>Do you know a way that I can iterate the files and get it one by one?

Implement a NextFileFilter that extends FileFilter and
feed it to File.listFiles(nextFileFilter). But I expect the
JVM will ultimately fetch the entire file list before being
able to determine which is the 'next' file.

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Andrew Thompson
http://www.athompson.info/andrew/

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Christian - 07 Aug 2007 12:54 GMT

jaja schrieb:

> On Aug 7, 12:29 pm, Thomas Fritsch <i.dont.like.s...@invalid.com>
> wrote:
[quoted text clipped - 10 lines]
> Do you know a way that I can iterate the files and get it one by one?
> Thanks.

Are you really shure you need this kind of optimization?

usual directorys should have less than 10k files in them which should
mean less than 500 kiB of Memory, any problem with that?

if you have more than a 100k files per dir and need to have multiple
lists of such large directorys .. well.. first I would recommend you to
check the program that produced these horrible mess of files as this
could crash your filesystem .. or at least give it a hard time.

Christian

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Roedy Green - 07 Aug 2007 14:06 GMT

> How can I iterate the files inside a directory, like FindNextFile in
>Win32.
> I don't want to use File.list() which returns me a list of all files.

.list is the Java idiom. It is probably considerably more efficient
to wind up the JNI .list method only once to get them all.

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Roedy Green Canadian Mind Products
The Java Glossary
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Roedy Green - 07 Aug 2007 18:04 GMT

>.list is the Java idiom. It is probably considerably more efficient
>to wind up the JNI .list method only once to get them all.

There is a considerable overhead crossing the blood-brain barrier into
the JNI world. .list has to cross it only once. findNextFile would
have to cross it N times.

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Roedy Green Canadian Mind Products
The Java Glossary
http://mindprod.com

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Java equivalent for MFC findnextfile

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