Need zlib-devel installed.

gcj --main=pkg.MainClass file.java




C++ calls to Java:
http://www-ti.informatik.uni-tuebingen.de/~thiele/cni/
    Change getMethod() to getDeclaredMethod().
    Add -lz to the static g++ command.
    Make *.class file any way you want (may use gcj).
    g++ -static java.cpp -o java -lgcj -ldl -lpthread -lz