Re: CLI Java Glitch

From:
Nigel Wade <nmw-news@ion.le.ac.uk>
Newsgroups:
comp.lang.java.programmer
Date:
Thu, 23 Jun 2011 15:18:57 +0100
Message-ID:
<96h0aiFf86U1@mid.individual.net>
On 22/06/11 20:00, Tom Anderson wrote:

On Wed, 22 Jun 2011, Nigel Wade wrote:

On 21/06/11 22:49, Tom Anderson wrote:

On Tue, 21 Jun 2011, Esmond Pitt wrote:

On 21/06/2011 8:09 AM, Martin Gregorie wrote:

The Java language system does case-sensitive comparisons between class
names and the files that contain them when checking that a class name
matches the file name that contains it


Nitpicking, but it doesn't really do that, does it. It opens a
.class file of the name the user specified, loads the class(es) it
contains, and tries to find the classname it was looking for among
those classes. It doesn't explicitly compare the filename and the
classname. The operating system gave it HelloWorld.class in response
to 'helloworld.class' because that's how the OS file system happened
to work.


The way Java does this at the moment means that 'java helloworld',
where there is no class 'helloworld', does different things on
Windows depending on whether there is a class HelloWorld, hElLoWoRlD,
HelloworlD, etc.


Does it? What different thing does it do?


To clarify, i meant that it does different things in these three
situations:

(1) helloworld exists
(2) HelloWorld, hElLoWoRlD, HelloworlD, or similar exists
(3) no class case-insensitively called helloworld exists

I think that cases (2) and (3) should do the same thing. Or, as you
describe it:

Java actually throws ClassNotFoundException in all cases, on all OS,
just as it should. The only difference is that in a case-insensitive
filesystem Java actually opens the case-insensitive filename before it
discovers that it does not contain the class required. On
case-sensitive filesystems the correct case filename won't be found.
The actual result is the same in both cases, a ClassNotFoundException.


Now, this is where i think i've gone wrong. Back when i used Windows,
java did *not* do the same thing in cases (2) and (3). For the
nonexistent file in (3), it would throw a NoClassDefFoundError. But for
the misnamed file in (2), it would throw something else - a
ClassFormatError, i think.

It seems that this has been fixed without me noticing, and i failed to
interpret Gene's original post correctly. If this is the case, then i
withdraw my complaint entirely!

tom


Well, I was testing on Windows 7 with NTFS (that's the only Windows
system I have to hand, I don't normally use Windows). It may well be
different on other version of Windows, or with vFAT.

--
Nigel Wade

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