Java update broke a Java app?

S. Dale Morrey sdalemorrey at
Fri Nov 18 12:14:28 MST 2011

> Yes, it is possible.  Is your wife using Windows?  Does she launch the app
> with a shortcut, or does she just double-click on a .jar file?  When you
> run "java --version" from a command-prompt, what version is reported (I'm
> assuming, it will say that it is Java 6 and not 7)?

Actually that's a good point, we both bought a couple of new Windows 7
laptops a couple of weeks ago.  And yes she just double clicks the jar
file.  I'll ask her the output of java --version when I get home
I wonder how you set the default JVM for Win7 if it turns out to be Java 6?
Win 7 admin isn't exactly my cup of tea.

> Java is backward compatible, but not forward.  A Java 6 JRE doesn't know
> how to read .class files that were compiled with a Java 7 compiler.  That
> is the most likely explanation.
> -Bryan

I've always written to Java 5 or 6 and never tried 7, but I do
remember a couple of times running a Java 5 app on a 6 machine and
having it /puke on itself.  Seemed like the message was quite
articulate about the issue.  On the other hand, my wife's response
thus far is something along the lines of... "It's throwing some sort
of error, please fix it."  Didn't really think that gave me much
leverage to ask more detailed questions.  At least not if I want to
eat tonight :)

I'm pretty sure she just clicks the .jar to launch it.

Wonder if this would have been a problem if they had gone a jnlp / web
start app.

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