Hi, I tried to implement a javaFX class which extends an Application. This class runs without problems in BlueJ, but if I try to use this class as an "other class" in Greenfoot and start the javaFX Application greenfoot produces an error, also the Application Window is shown correctly. Greenfoot stops working and the Debugger shows an sun.misc.Unsafe.park. I have to restart Greenfoot to go on working. Do you have any solutions for my problem? Thanks a lot for your help.