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Date: Mon, 9 May 2011 17:42:03 +0000 (UTC)
From: "Sebb (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (IO-271) FileUtils.copyDirectory should be able
 to handle arbitrary number of files
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    [ https://issues.apache.org/jira/browse/IO-271?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13030828#comment-13030828 ] 

Sebb commented on IO-271:
-------------------------

As already noted, listFiles() uses a private File constructor to create the File instances.
This is able to bypass the normalisation which the public ctors have to perform, so list() + new File() is less efficient than listFiles().

By the way, most OSes will have a backup tool which is likely to be considerably more efficient than Ant or Commons IO.

> FileUtils.copyDirectory should be able to handle arbitrary number of files
> --------------------------------------------------------------------------
>
>                 Key: IO-271
>                 URL: https://issues.apache.org/jira/browse/IO-271
>             Project: Commons IO
>          Issue Type: Improvement
>          Components: Utilities
>    Affects Versions: 2.0.1
>            Reporter: Stephen Kestle
>            Priority: Minor
>
> File.listFiles() uses up to a bit over 2 times as much memory as File.list().  The latter should be used in doCopyDirectory where there is no filter specified.
> This memory usage is a problem when copying directories with hundreds of thousands of files.
> I was also thinking of the option of implementing a file filter (that could be composed with the inputted filter) that would batch the file copy operation; copy the first 10000 (that match), then the next 10000 etc etc.
> Because of the lack of ordering consistency (between runs) of File.listFiles(), there would need to be a final file filter that would accept files that have not successfully been copied.
> I'm primarily concerned about copying into an empty directory (I validate this beforehand), but for general operation where it's a merge, the modification date re-writing should only be done in the final run of copies so that while batching occurs (and indeed the final "missed" filtering) files do not get copied if they have been modified after the start time. (I presume that I'm reading FileUtils correctly in that it overrides files...)

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