javafx : PieChart with mouse click chart

1.Main.java

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


public class Main extends Application {
	@Override
	public void start(Stage primaryStage) {
		try {
			Parent root = FXMLLoader.load(getClass().getResource("Main.fxml"));
			Scene scene = new Scene(root,500,300);
			scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
			primaryStage.setScene(scene);
			primaryStage.show();
		} catch(Exception e) {
			e.printStackTrace();
		}
	}
	
	public static void main(String[] args) {
		launch(args);
	}
}

2.Main.fxml

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.chart.PieChart?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.text.Font?>

<AnchorPane minHeight="300.0" prefWidth="500.0" xmlns="http://javafx.com/javafx/9.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="application.MainController">
   <children>
      <PieChart fx:id="pi" layoutX="14.0" layoutY="14.0" prefHeight="267.0" prefWidth="325.0" title="PieChart" />
      <Button layoutX="390.0" layoutY="47.0" mnemonicParsing="false" onAction="#btn" text="Button" />
      <Label fx:id="label" layoutX="390.0" layoutY="90.0" prefHeight="17.0" prefWidth="69.0" text="Label">
         <font>
            <Font size="18.0" />
         </font>
      </Label>
   </children>
</AnchorPane>

3.MainController.java

import javafx.fxml.FXML;
import javafx.scene.chart.PieChart;
import javafx.scene.chart.PieChart.Data;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.control.Label;
import javafx.scene.input.MouseEvent;

public class MainController{
	@FXML public PieChart pi;
	@FXML public Label label;
	
	public void btn(ActionEvent event) {
		ObservableList<Data> list = FXCollections.observableArrayList(
				new PieChart.Data("java", 50),
				new PieChart.Data("python", 25),
				new PieChart.Data("c++", 20),
				new PieChart.Data("c#", 5)
				);
		pi.setData(list);
		
		for(PieChart.Data data : pi.getData()) {
			data.getNode().addEventHandler(MouseEvent.MOUSE_CLICKED, new EventHandler<MouseEvent>() {

				@Override
				public void handle(MouseEvent event) {
					label.setText(String.valueOf(data.getPieValue()) + "%");
				}
				
			});
		}
	}
}