import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;


public class Main extends Application {

    private static Controller controller;

    @Override
    public void start(Stage primaryStage) throws Exception{
        FXMLLoader loader = new FXMLLoader(getClass().getResource("/sample.fxml"));
        Parent root = loader.load();
        controller = loader.getController();

        primaryStage.setTitle("ugly javafx");
        primaryStage.setScene(new Scene(root, 350, 400));
        primaryStage.show();

        doSomething();
    }

    private void doSomething() {
        controller.sendBtn.setText("aaa");
    }

    public static void main(String[] args) {
        launch(args);
    }

}