80008304 is the latest version of SNX. It is available since R81.10 Jumbo take 55.
SNX itself doesn't require Java runtime. It is needed for deployment and control from Mobile Access Portal page. See sk113410 for more details. Pay attention to supported Java versions and editions.
If you see "Java unavailable" message, it means that Mobile Access Portal Agent can't detect installed Java. Check output of following command in CMD:
If you see Java version. try to re-install "Check Point Mobile Access Portal Agent". If it doesn't help - better open ticket with support.