error starting java .jar app - classpath issue?

[Gordon Pedersen <gordon@visi.com>]

This is likely a very simple issue.  I've never tried to run a
java .jar library on debian before.  

I wonder if it may just be a matter of learning how to correctly
setting the CLASSPATH before issuing the java command on .jar
libraries held in /usr/share/java/.  I could not find any
clear guidance about the usual CLASSPATH practice on debian. 

For all commands discussed below, no CLASSPATH variable has been
defined.

(I run sarge.  Java is from blackdown j2re1.4 and j2sdk1.4.
Installed without a hitch.)

App in question is a timekeeper program.  See
http://www.taubler.com/timebox/.

No errors if I switch to the .jar file directory and issue this
command:

	$ java -jar tt.jar

But if if try either of the following commands from an outside
directory, the errors shown below commands appear:

	$ java -jar /usr/share/java/tt.jar
	$ java -classpath /usr/share/java/tt.jar -jar /usr/share/java/tt.jar

Exception in thread "main" java.lang.NullPointerException
        at javax.swing.ImageIcon.<init>(ImageIcon.java:161)
        at com.taubler.timebox.submit.SubmitExtensionWidget.<init>(SubmitExtensionWidget.java:16)
        at com.taubler.timebox.submit.SubmitManager.<init>(SubmitManager.java:52)
        at com.taubler.timebox.TimeTracker.<init>(TimeTracker.java:54)
        at com.taubler.timebox.TimeTracker.main(TimeTracker.java:1115)

Thanks.

Gordon
-- 
Gordon Pedersen
St Paul,  Minnesota,   USA