Unsade operation in my first JavaFX application
===

Please have a look at my first JavaFX application code

    package helloworld;
    
    import javafx.application.*;
    import javafx.stage.*;
    import javafx.event.*;
    import javafx.scene.Scene;
    import javafx.scene.control.Button;
    import javafx.scene.layout.StackPane;
    
    public class HelloWorld2 extends Application
    {
        @Override
        public void start(Stage stage)
        {
            stage.setTitle("Hello World");
            
            Button btn = new Button();
            btn.setText("Hello");
            btn.setOnAction(new Action());
            
            StackPane pane = new StackPane();
            pane.getChildren().add(btn);
            
            stage.setScene(new Scene(pane, 300,250));
            stage.show();
        }
        
        private class Action implements EventHandler
        {
    
            @Override
            public void handle(Event arg0) 
            {
                System.out.println("JavaFX World");
            }
            
        }
        
        public static void main(String[]args)
        {
            launch(args);
        }
    }

I am getting "Unsafe Operation" warning when I run this. Application runs without any exceptions. I believe unsafe thing is coming because I have to put <ActionEvent> keyword in some place, but I don't know where. Please help!