Compiled java classes contain a version number put there by the compiler used.
The JavaVM you're trying to load the classes into, can't understand the particular class version created by the compiler.

I use Java 1.4 to compile which uses the class version 48.
It looks like the JavaVM you are trying to use is older then Java 1.4 or the Java installation is broken or mixed with other Java versions.

Gregor

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