When running the showImage() method in OpenCV 3.0 or greater, an exception is returned:
Exception in thread "Thread-0" java.lang.NoClassDefFoundError: org/opencv/highgui/Highgui
This is because Highgui has been removed in opencv 3.0 and split into two different packages - see this stackexchange for more details http://stackoverflow.com/questions/25059576/highgui-is-missing-from-opencv-3-0-0-jar