So this worked in the example from javafx when My pc had jdk 1.7.0 so this may be the new version of FX in java8 however;
I get a nice stack-trace
jf
If Any One does not fix the problem by following answers, The simple way is to create new fxml Empty class then click on edit of the fxml causin the problem and copy the xml code to the new class . Go to the start() methode, change the:
Pane mainPane = FXMLLoader.load(getClass().getResource("main.fxml"));
to
Pane mainPane = FXMLLoader.load(getClass().getResource("newClass.fxml"));