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From "Sebb (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (IO-340) The use of file.exists() is failure prone. Where file.exists() is checked, it should be replaced with the following dual check: exists = ( file.exists() || file.length()>0 )
Date Sat, 04 Aug 2012 09:16:02 GMT

    [ https://issues.apache.org/jira/browse/IO-340?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13428589#comment-13428589
] 

Sebb commented on IO-340:
-------------------------

Strange that file.exists() should not cause a handle refresh whereas it appears file.length()
does.

But it's not a full solution as file.length() can be zero for a file that does exist.
Perhaps it works for you because none of your files are empty?
Might be better to check for lastModified != 0, as that would potentially work with empty
files too.

Nevertheless, all code should still allow for the fact that files can appear/disappear between
the check and the next file operation. Potentially even on local storage if a hardware fault
occurs.


                
> The use of file.exists() is failure prone. Where file.exists() is checked, it should
be replaced with the following dual check:  exists = ( file.exists() || file.length()>0
)
> ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: IO-340
>                 URL: https://issues.apache.org/jira/browse/IO-340
>             Project: Commons IO
>          Issue Type: Bug
>          Components: Utilities
>    Affects Versions: 2.5, 3.x
>         Environment: All
>            Reporter: Wilf Middleton
>              Labels: File, exists, false
>             Fix For: 2.5, 3.x
>
>   Original Estimate: 24h
>  Remaining Estimate: 24h
>
> The use of file.exists() is failure prone. In many cases the jvm can report that a file
does not exist even when it does. This is due to the caching in the operating system.
> Since file.exists() is prone to report false values, a second check can and should be
made to file.length()>0.
> Where file.exists() is checked, it should be replaced with the following dual check:
 
> A file more reliably exists if:  file.exists() || file.length()>0
> Then if the file does not exist, file.length will be 0.

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