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From: Stefan Bodewig <bodewig@apache.org>
To: user@ant.apache.org
Subject: Re: WELCOME to user@ant.apache.org
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Date: Mon, 15 Jun 2015 05:51:17 +0200
In-Reply-To: 
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	(Christopher BROWN's message of "Sun, 14 Jun 2015 21:27:15 +0200")
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On 2015-06-14, Christopher BROWN wrote:

> Since Java SE 7, URLClassLoader defines a "close()" method which may be
> useful in the specific case mentioned:
> http://docs.oracle.com/javase/7/docs/api/java/net/URLClassLoader.html#close()

This won't help if the file in question is on the system classloader or
the classloader is going to be used later.

> As for the more general case of Windows locking files from Java, as I
> understand it, it's because the underlying file descriptor use to read from
> or write to files is only release when the associated stream is garbage
> collected (the logic is in the "finalize()" method).  In my own code, I
> have a utility "delete(File)" method that tries to delete the file, and if
> it fails (on a Windows system) will loop with 10 millisecond sleep
> intervals, on the second and last iterations attempting System.gc() to
> force finalization, and it is seems to be a robust workaround in practice.

Ant has similar code.  In 1.7.0 it was restricted to specific cases like
the Delete task, nowadays it is a helper method (tryHardToDelete in
FileUtils) that has been factored out and is used whenever a task wants
to delete a file.

Unfortunately it doesn't help for all cases (like files on the
classloader) and that's when the deleteOnExit work around we've added
comes into play.

Stefan

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