Re: CLI Java Glitch

From	Nigel Wade <nmw-news@ion.le.ac.uk>
Newsgroups	comp.lang.java.programmer
Subject	Re: CLI Java Glitch
Date	2011-06-22 11:54 +0100
Message-ID	<96dvubFalpU1@mid.individual.net> (permalink)
References	<meevv65a675khs5c9goa9sp6f2hotf1321@4ax.com> <itogee$k8r$1@localhost.localdomain> <4dffe2ea$0$57121$c30e37c6@exi-reader.telstra.net> <alpine.DEB.2.00.1106212245430.6476@urchin.earth.li>

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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?

As far as a case-insensitive OS/filesystem is concerned, they would all
appear as the same file. If Java asked for any of those names from the
filesystem it would get the one file which did exist for any of the
class names. It would then look in that file for the class it required.
If the class did not exist in that file it would throw the
ClassNotFoundException. It cannot do anything else because the
OS/filesystem simply will not allow 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.

> 
> That seems pretty shoddy to me. If you're a case-sensitive program
> running on a case-insensitive operating system, i think it falls on you
> to pay special attention to case in your dealings with that system: when
> java opens a class file, it ought to check that the name of the file
> it's opened actually has the right case, and if it doesn't, discard it,
> and act as if it had got a file not found error from the operating system.
> 
> tom
> 

But Java cannot do this. On a case-insensitve OS/filesystem it simply
may not be possible for a file to exist called HelloWorld.class.

Java is not doing anything wrong. The user is, in assuming that because
the OS/filesystem is case-insensitive that Java is also. The java
command syntax is "java <ClassName>" not "java <filename>". That class
name is case sensitive, no matter how brain dead the OS or filesystem.
If you ask Java to run the class helloworld when your class is actually
HelloWorld, you have asked it to do the wrong thing. Java is perfectly
correct in telling you this.

If you ask Java to run the class HelloWorld, it does so even on a
case-insensitive system such as that of the OP. Even if the file is
called helloworld.class Java still manages to do the right thing.

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Thread

CLI Java Glitch Gene Wirchenko <genew@ocis.net> - 2011-06-20 14:24 -0700
  Re: CLI Java Glitch Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-06-20 14:48 -0700
  Re: CLI Java Glitch Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-06-20 18:49 -0300
  Re: CLI Java Glitch Martin Gregorie <martin@address-in-sig.invalid> - 2011-06-20 22:09 +0000
    Re: CLI Java Glitch Esmond Pitt <esmond.pitt@bigpond.com> - 2011-06-21 10:16 +1000
      Re: CLI Java Glitch Tom Anderson <twic@urchin.earth.li> - 2011-06-21 22:49 +0100
        Re: CLI Java Glitch Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-06-21 15:11 -0700
          Re: CLI Java Glitch Gene Wirchenko <genew@ocis.net> - 2011-06-21 16:37 -0700
            Re: CLI Java Glitch Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-06-21 17:54 -0700
            Re: CLI Java Glitch lewbloch <lewbloch@gmail.com> - 2011-06-22 09:02 -0700
              Re: CLI Java Glitch Gene Wirchenko <genew@ocis.net> - 2011-06-22 10:12 -0700
                Re: CLI Java Glitch Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-06-22 10:39 -0700
          Re: CLI Java Glitch Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-06-22 09:50 -0700
          Re: CLI Java Glitch Tom Anderson <twic@urchin.earth.li> - 2011-06-22 19:44 +0100
            Re: CLI Java Glitch Michael Wojcik <mwojcik@newsguy.com> - 2011-06-23 12:31 -0400
              Re: CLI Java Glitch Tom Anderson <twic@urchin.earth.li> - 2011-06-23 23:04 +0100
                Re: CLI Java Glitch Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-06-23 21:40 -0700
                Re: CLI Java Glitch Michael Wojcik <mwojcik@newsguy.com> - 2011-06-24 09:43 -0400
          Re: CLI Java Glitch Michael Wojcik <mwojcik@newsguy.com> - 2011-06-23 12:24 -0400
            Re: CLI Java Glitch Gene Wirchenko <genew@ocis.net> - 2011-06-23 14:32 -0700
            Re: CLI Java Glitch lewbloch <lewbloch@gmail.com> - 2011-06-24 09:12 -0700
              Re: CLI Java Glitch Bent C Dalager <bcd@pvv.ntnu.no> - 2011-06-24 22:49 +0000
                Re: CLI Java Glitch Gene Wirchenko <genew@ocis.net> - 2011-06-26 20:29 -0700
        Re: CLI Java Glitch Gene Wirchenko <genew@ocis.net> - 2011-06-21 16:29 -0700
        Re: CLI Java Glitch Nigel Wade <nmw-news@ion.le.ac.uk> - 2011-06-22 11:54 +0100
          Re: CLI Java Glitch Gene Wirchenko <genew@ocis.net> - 2011-06-22 10:16 -0700
            Re: CLI Java Glitch Patricia Shanahan <pats@acm.org> - 2011-06-22 11:06 -0700
              Re: CLI Java Glitch Gene Wirchenko <genew@ocis.net> - 2011-06-22 11:46 -0700
                Re: CLI Java Glitch Gene Wirchenko <genew@ocis.net> - 2011-06-22 12:50 -0700
                Re: CLI Java Glitch Nigel Wade <nmw-news@ion.le.ac.uk> - 2011-06-23 15:23 +0100
                Re: CLI Java Glitch Gene Wirchenko <genew@ocis.net> - 2011-06-23 08:58 -0700
                Re: CLI Java Glitch lewbloch <lewbloch@gmail.com> - 2011-06-24 08:58 -0700
                Re: CLI Java Glitch Gene Wirchenko <genew@ocis.net> - 2011-06-24 11:36 -0700
                Re: CLI Java Glitch Paul Cager <paul.cager@googlemail.com> - 2011-06-22 14:45 -0700
                Re: CLI Java Glitch Tom Anderson <twic@urchin.earth.li> - 2011-06-22 23:29 +0100
                Re: CLI Java Glitch Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-06-22 18:08 -0700
                Re: CLI Java Glitch Tom Anderson <twic@urchin.earth.li> - 2011-06-23 23:20 +0100
                Re: CLI Java Glitch Esmond Pitt <esmond.pitt@bigpond.com> - 2011-06-24 10:28 +1000
                Re: CLI Java Glitch Tom Anderson <twic@urchin.earth.li> - 2011-06-25 22:58 +0100
                Re: CLI Java Glitch Gene Wirchenko <genew@ocis.net> - 2011-06-26 20:31 -0700
                Re: CLI Java Glitch lewbloch <lewbloch@gmail.com> - 2011-06-24 09:00 -0700
          Re: CLI Java Glitch Tom Anderson <twic@urchin.earth.li> - 2011-06-22 20:00 +0100
            Re: CLI Java Glitch Nigel Wade <nmw-news@ion.le.ac.uk> - 2011-06-23 15:18 +0100
        Re: CLI Java Glitch Esmond Pitt <esmond.pitt@bigpond.com> - 2011-06-23 11:40 +1000
          Re: CLI Java Glitch Esmond Pitt <esmond.pitt@bigpond.com> - 2011-06-23 20:21 +1000
          Re: CLI Java Glitch Gene Wirchenko <genew@ocis.net> - 2011-06-23 09:00 -0700
            Re: CLI Java Glitch Esmond Pitt <esmond.pitt@bigpond.com> - 2011-06-24 10:24 +1000
    Re: CLI Java Glitch Tom Anderson <twic@urchin.earth.li> - 2011-06-21 22:52 +0100
  Re: CLI Java Glitch Jeff Higgins <jeff@invalid.invalid> - 2011-06-20 19:11 -0400
    Re: CLI Java Glitch Lew Bloch <lewisbloch@google.com> - 2011-06-20 16:25 -0700
      Re: CLI Java Glitch Jeff Higgins <jeff@invalid.invalid> - 2011-06-20 19:45 -0400
        Re: CLI Java Glitch Lew Bloch <lewisbloch@google.com> - 2011-06-20 18:28 -0700
        Ping: Lew Bloch Jeff Higgins <jeff@invalid.invalid> - 2011-06-20 23:26 -0400
          Re: Ping: Lew Bloch Lew Bloch <lewisbloch@google.com> - 2011-06-21 10:25 -0700
            Re: Ping: Lew Bloch Jeff Higgins <jeff@invalid.invalid> - 2011-06-21 14:36 -0400
      Re: CLI Java Glitch Patricia Shanahan <pats@acm.org> - 2011-06-20 17:02 -0700
        Re: CLI Java Glitch Jeff Higgins <jeff@invalid.invalid> - 2011-06-20 20:37 -0400
          Re: CLI Java Glitch Jeff Higgins <jeff@invalid.invalid> - 2011-06-20 20:44 -0400
            Re: CLI Java Glitch Tom Anderson <twic@urchin.earth.li> - 2011-06-21 22:45 +0100
  Re: CLI Java Glitch Roedy Green <see_website@mindprod.com.invalid> - 2011-06-20 16:55 -0700
    Re: CLI Java Glitch Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-20 20:44 -0400
      Re: CLI Java Glitch Gene Wirchenko <genew@ocis.net> - 2011-06-20 19:26 -0700
      Re: CLI Java Glitch Paul Cager <paul.cager@googlemail.com> - 2011-06-21 02:34 -0700
        Re: CLI Java Glitch Silvio <silvio@moc.com> - 2011-06-21 16:50 +0200
        Re: CLI Java Glitch "Gavino" <invalid@invalid.invalid> - 2011-06-21 21:35 +0200
      Re: CLI Java Glitch Roedy Green <see_website@mindprod.com.invalid> - 2011-06-21 11:59 -0700
        Re: CLI Java Glitch Gene Wirchenko <genew@ocis.net> - 2011-06-21 13:03 -0700
          Re: CLI Java Glitch BGB <cr88192@hotmail.com> - 2011-06-21 14:21 -0700
  Re: CLI Java Glitch Gene Wirchenko <genew@ocis.net> - 2011-06-20 19:29 -0700
  Re: CLI Java Glitch Tom Anderson <twic@urchin.earth.li> - 2011-06-21 22:42 +0100
    Re: CLI Java Glitch Gene Wirchenko <genew@ocis.net> - 2011-06-21 14:48 -0700
  Re: CLI Java Glitch Jeff Higgins <jeff@invalid.invalid> - 2011-06-21 21:52 -0400
    Re: CLI Java Glitch Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-06-22 07:56 -0300
      Re: CLI Java Glitch Jeff Higgins <jeff@invalid.invalid> - 2011-06-22 08:02 -0400
        Re: CLI Java Glitch Gene Wirchenko <genew@ocis.net> - 2011-06-22 10:18 -0700
          Re: CLI Java Glitch Jeff Higgins <jeff@invalid.invalid> - 2011-06-22 15:01 -0400
            Re: CLI Java Glitch Gene Wirchenko <genew@ocis.net> - 2011-06-22 12:54 -0700
          Re: CLI Java Glitch Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-06-22 18:52 -0300
          Re: CLI Java Glitch Michael Wojcik <mwojcik@newsguy.com> - 2011-06-23 15:13 -0400

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