Example code and documentation on using Firmata communication in native Java
Maybe this can work for you.
Some months ago i used RXTXcomm library [1] to send Arduino data to a Program i made in java and store in in a file, it works fine with some issues:


I made the Java programm in linux but just works in java 6, so in the windows pc of the client i installed that version, i don't know if works with java7 or java8 in windows.
Java programm reads data from Arduino sketch with Serial.print() function, Arduino continously is using this function, i lose some data, so i had to put a short delay to java programm get all data send by Arduino.


[1] http://rxtx.qbang.org/wiki/index.php/Main_Page