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From: Daku on 30 Dec 2009 07:50
Could some Java guru please kindly help ? I am porting
an application from Linux to Windows (with Active
Directory running), and getting into very odd problems.
I am using Eclipse IDE.

I want to open a directory as:
File infile = new File ("C:/temp");
......
Then :
if(infile != null)
{
try
[
infile.createNewFile();
}
catch(IOException ioe)
{
}

if(infile != null && infile.isDirectory())
{ // Do some processing
}

The test -- infile != null passes, but infile.isDirectory()
does not. All processing inside the if block depends
on infile being a directory.

Any hints suggestions would be of immense help.


From: Eric Sosman on 30 Dec 2009 08:24
On 12/30/2009 7:50 AM, Daku wrote:
> Could some Java guru please kindly help ? I am porting
> an application from Linux to Windows (with Active
> Directory running), and getting into very odd problems.
> I am using Eclipse IDE.
>
> I want to open a directory as:
> File infile = new File ("C:/temp");
> .....
> Then :
> if(infile != null)

Unless you've set infile=null somewhere in the "....."
part, the condition is guaranteed to be true. What are you
trying to test here? Do you realize that the test you're
actually making says nothing at all about what is or is not
on the file system?

> {
> try
> [

... proving that the code you've showed us cannot possibly
be the code you're actually using. If the problems and remedies
people point out in what you've shown don't help with the
difficulty you're having, it's entirely your fault. "Doctor,
I have this terrible pain in my ankle -- whenever I swallow."

> infile.createNewFile();

What are you trying to do? This will (try to) create a
new file if none exists already, or will leave an existing
file untouched. And it will report what it did or didn't do
by returning a true or false value -- but since you ignore
that value, what's the point? You can be sure that a file
exists, but you can also be sure that if it exists because
this call created it, then the newly-created file will *not*
be a directory.

> }
> catch(IOException ioe)
> {

Bad Daku! Bad! Bad! Bad!

> }
>
> if(infile != null&& infile.isDirectory())

Again, the first part of the test is silly. The second
will succeed only if the file existed before your code ran
(because if it didn't, the new file you create will be an
ordinary data file and not a directory).

> { // Do some processing
> }
>
> The test -- infile != null passes, but infile.isDirectory()
> does not.

Exactly as expected. Why do you find this surprising?

> All processing inside the if block depends
> on infile being a directory.
>
> Any hints suggestions would be of immense help.

What are you trying to do? I can offer help like "Buy
low, sell high" but unless I know your goal it's hard to
be more specific.

... and none of this seems to have anything at all to
do with Active Directory. So, again: What's your goal?

--
Eric Sosman
esosman(a)ieee-dot-org.invalid
From: Patricia Shanahan on 30 Dec 2009 08:39
Daku wrote:
> Could some Java guru please kindly help ? I am porting
> an application from Linux to Windows (with Active
> Directory running), and getting into very odd problems.
....
>
> Any hints suggestions would be of immense help.
>
>

Lew has dealt with a lot of the issues. I have a few supplementary comments.

The Java I/O library *tries* to give you useful hints about what
happened during your calls to it, through return values and exceptions.
You seem to be firmly ignoring those hints.

Your code is configuration dependent because it does different things
based on whether a directory exists or not. You need to rethink that to
make the code portable. If you really want to create c:/Temp if it does
not exist, you need to change the createNewFile to mkDir.

However, many users would not like an application creating a new
directory at the top level. If you just want to put some files in a
suitable temporary directory, I suggest using one of the createTempFile
methods. The I/O library handles the problem of locating the
conventional temporary file directory for you.

Patricia
From: Lew on 30 Dec 2009 09:04
Patricia Shanahan wrote:
> ...
Eric
> has dealt with a lot of the issues.

But I'm flattered by the comparison.

--
Lew
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