according to JRI Javadoc....
Only one Rengine Instance can be used, and Rengine.end() function has some problems...
you should not use code like this
Rengine engine = new Rengine(new String[] {"--vanilla"}, false, null);
you can use Rengine with this code
Rengine engine = Rengine.getMainEngine();
if(engine == null)
engine = new Rengine(new String[] {"--vanilla"}, false, null);