I did this using the rubygem Java-Ruby-Bridge. I did this because I was having problems with JRuby and wanted to execute my class from within Ruby.
Here is a simple way to do it, as long as you remember the classpath.
require 'rjb' Rjb::load(classpath = '../../TestJava/bin', jvmargs=) test = Rjb::import('Test') c = test.new c.foo3
This way I was able to invoke a web camera testing program written in java with a few environment variable calls
ENV['CLASSPATH'] = '../../JavaRobots/dist/javarobots.jar;../../JavaRobotsLib/jai_core.jar;../../JavaRobotsLib/jai_codec.jar'
test = Rjb::import('com.scottpreston.javarobot.vision.ImageViewer') c = test.new("c:\\temp\\fcover.jpg") #default_close_operation = JFRAME::EXIT_ON_CLOSE sleep 5