Are jgnat tools compatible with Java 2?

[peterm@resmed.com.au (Peter Milliken)]

I am just starting to explore jgnat-1.1p(NT) and found the first thing
I attempted failing. I have Sun's j2sdk1.4.0_01 loaded on my computer,
so I attempted the example shown in the jgnat user's guide for
creating Ada package specs from Java .jar files with (Chapter 6):

jvm2ada rt.jar

The command failed. The full sequence is:

roebourne#1(/c/j2sdk1.4.0_01/jre/lib)$ jvm2ada rt.jar
jvm2ada: Bad class file: bad minor version
[exited with 4]

Since I was able to successfully execute the "hello world" program
provided in the "Getting Started" section, I assume that this is most
likely a compatability problem with the tool set that comes with jgnat
1.1p.

Is there anyway around this problem? Has anyone managed to
successfully develop code using jgnat for Java 2 that interfaces to
existing Java 2 classes? I assume that to do this, you would need to
generate Ada package spec's for the Java classes.....

Thanks
Peter