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You can get the Java interface from pythiaJava.tar.gz.
Put it somewhere and extract with tar -xvf <filename.tar.gz>
Please also make sure that you have a proper version of a Java compiler with the JNI interface and that the environment variable $JDK_ROOT points to it.
Make sure the LD_LIBRARY_PATH variable contains the current directory. (.)
Make sure you have the pythia version you want
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