import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Alert;
import javafx.scene.layout.VBox;
 
public class App extends Application {
    public static void main(String[] args) {
        launch(args);
    }
 
    @Override
    public void start(Stage primaryStage) throws Exception {
        Button showButton = new Button("Mutat");
        Alert alert = new Alert(Alert.AlertType.INFORMATION);        
        showButton.setOnAction(e -> {
            alert.setTitle("Címsor szöveg");
            alert.setHeaderText("Fejrész szöveg");
            alert.setContentText("Üzenet");
            alert.showAndWait();
        });
 
        VBox vbox = new VBox();
        vbox.setPadding(new Insets(10, 10, 10, 10));
        vbox.setSpacing(10);
        vbox.getChildren().add(showButton);
 
        Scene scene = new Scene(vbox, 300, 250);
        primaryStage.setScene(scene);
 
        primaryStage.show();
    }
 
}