Now in controller files we have multiple instances of @FXML decorator. It will be better where decorator @FXML will include all lines(section) to the empty new line.

Example:
Now:

@FXML
Button example_button;
@FXML
Label example_label;

My suggestion:
// section from FXML file
@FXML
Button example_button;
Label example_label;
HBox example_hbox;

// normal java code section
String str;
Object object;