[news.eclipse.newcomer] Re: Compiling for older version of java

[Mark Dexter <dextercowley@xxxxxxxxx>]

joel wrote:
> Mark Dexter wrote:
>
> > Hi Joel. The application hangs, both when I try to run the Jar and 
> > when I try to run JChessboard.java from inside Eclipse. It hangs on 
> > line 955 when I debug. It draws a transparent frame and hangs. Am I 
> > missing something needed to run the app? Once I get it working here, I 
> > can play with it on Linux. Thanks. Mark
>
> Mark:
>
> That's a bug that pops up occasionally - haven't figured out why just 
> yet. Just kill the java or javaw process and try it again.  It will start.
>
> --Joel
Hi Joel. It appears to work as expected on my Windows and Linux systems. 
That is, if I have Windows / Preferences / Java / Compiler / Compiler 
compliance level 6.0, create a jar (e.g. jchessboad16.jar) and then try 
to run it on my Linux machine (which has 1.5 JRE), I get the message 
"Exception in thread "main" java.lang.UnsupportedClassVersionError: Bad 
version number in .class file". (Note that I don't have any 
project-specific settings, so the default preferences is the only 
relevant setting. If you have project-specific settings, I guess you 
would change those instead.)

If I change the compiler compliance level to 5.0, create a new Jar file, 
it works on my Linux machine. Both jar files execute on my Windows system.

So, as they say, "it works fine on my machine" (which is Eclipse 3.3.0). 
So it would appear to be something about your environment rather than 
something about the program. You could prove that by trying it with a 
simple hello world jar file. Hope this helps. Mark

P.S. The hang-up bug in the program does not seem to be consistent. On 
the Linux machine, I only got the Jar file to run correctly once out of 
several attempts. On my Windows system, it seems to work about 1/3 of 
the time.