Creating the following bash script fixed my issue:
export LD_LIBRARY_PATH="/usr/lib/jvm/java-7-openjdk-amd64/jre/lib/amd64/"
java -jar minecraft.jar
download the module and untar it. (http://www.linuxfoundation.org/collaborate/workgroups/networking/alx)
compile the module :
./scripts/driver-select alx
make
make install
modprobe alx