i have seen other answers but nothing have helped me
(sorry new to GUI only know basics of swing)
this is main class
package application;
imp
getClass().getClassLoader().getResource(...) will load a resource from a path relative to the classpath. Since you placed the FXML file in the application pacakge, you need:
Parent root=FXMLLoader.load(getClass().getClassLoader().getResource("application/Main.fxml"));
If you just use getClass().getResource(...), and do not prefix the path with /, it will load from a path relative to the current class. So
Parent root=FXMLLoader.load(getClass().getResource("Main.fxml"));
should also work.
Make sure that your FXML file is being exported to the build folder, along with the .class files.