BarChart with Label and refresh Data

BarChartwithLabelandRefresh

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import java.text.DecimalFormat;

import javafx.application.Application;
import javafx.beans.value.*;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Bounds;
import javafx.geometry.Pos;
import javafx.scene.*;
import javafx.scene.chart.*;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.layout.*;
import javafx.scene.paint.Color;
import javafx.scene.shape.*;
import javafx.scene.text.Text;
import javafx.stage.Stage;

/**
 * Displays a bar with a single series whose bars are different colors depending
 * upon the bar value. A custom legend is created and displayed for the bar
 * data. Bars in the chart are customized to include a text label of the bar's
 * data value above the bar.
 */
public class DynamicallyColoredBarChartWithLabel extends Application {
	
	Button button = new Button("Refresh");
	BarChart<String, Number> bc;

    @Override
    public void start(Stage stage) {
        final CategoryAxis xAxis = new CategoryAxis();
        xAxis.setLabel("Bars");
        final NumberAxis yAxis = new NumberAxis();
        yAxis.setLabel("Value");

        bc = new BarChart<>(xAxis, yAxis);
        bc.setLegendVisible(false);

        XYChart.Series series1 = new XYChart.Series();

        for (int i = 0; i < 10; i++) {
            final XYChart.Data<String, Number> data = new XYChart.Data("Value " + i, i);
            data.nodeProperty().addListener(new ChangeListener<Node>() {
                @Override
                public void changed(ObservableValue<? extends Node> ov, Node oldNode, final Node node) {
                    if (node != null) {
                        setNodeStyle(data);
                        displayLabelForData(data);
                    }
                }
            });
            series1.getData().add(data);
        }
        bc.getData().add(series1);

        LevelLegend legend = new LevelLegend();
        legend.setAlignment(Pos.CENTER);

        VBox chartWithLegend = new VBox();
        chartWithLegend.getChildren().setAll(bc, legend);
        VBox.setVgrow(bc, Priority.ALWAYS);
        chartWithLegend.getStylesheets().add(getClass().getResource("colored-chart.css").toExternalForm());
        stage.setScene(new Scene(chartWithLegend));
        stage.setMinHeight(400);
        stage.setMinWidth(400);
        stage.show();
    }

    /**
     * Change color of bar if value of i is <5 then red, if >5 then green if i>8
     * then blue
     */
    private void setNodeStyle(XYChart.Data<String, Number> data) {
        Node node = data.getNode();
        if (data.getYValue().intValue() > 8) {
            node.setStyle("-fx-bar-fill: -fx-exceeded;");
        } else if (data.getYValue().intValue() > 5) {
            node.setStyle("-fx-bar-fill: -fx-achieved;");
        } else {
            node.setStyle("-fx-bar-fill: -fx-not-achieved;");
        }
    }

    /**
     * places a text label with a bar's value above a bar node for a given
     * XYChart.Data
     */
    private void displayLabelForData(XYChart.Data<String, Number> data) {
        final Node node = data.getNode();
        final DecimalFormat df = new DecimalFormat( "$###,##0.00" );
        final Text dataText = new Text(df.format(data.getYValue()) + "");
        node.parentProperty().addListener(new ChangeListener<Parent>() {
            @Override
            public void changed(ObservableValue<? extends Parent> ov, Parent oldParent, Parent parent) {
                if(null!=parent)
                {
                	Group parentGroup = (Group) parent;
                	parentGroup.getChildren().add(dataText);
                }
            }
        });

        node.boundsInParentProperty().addListener(new ChangeListener<Bounds>() {
            @Override
            public void changed(ObservableValue<? extends Bounds> ov, Bounds oldBounds, Bounds bounds) {
                dataText.setLayoutX(
                        Math.round(
                                bounds.getMinX() + bounds.getWidth() / 2 - dataText.prefWidth(-1) / 2
                        )
                );
                dataText.setLayoutY(
                        Math.round(
                                bounds.getMinY() - dataText.prefHeight(-1) * 0.5
                        )
                );
            }
        });
        
        button.setOnAction(new EventHandler<ActionEvent>() {
			
			@Override
			public void handle(ActionEvent paramT) {
				bc.getData().clear();
				 XYChart.Series series1 = new XYChart.Series();

			        for (int i = 10; i < 20; i++) {
			        	
			            final XYChart.Data<String, Number> data = new XYChart.Data("Value " + i, 1.0 + (Math.random()*(10-1+1)));
			            data.nodeProperty().addListener(new ChangeListener<Node>() {
			                @Override
			                public void changed(ObservableValue<? extends Node> ov, Node oldNode, final Node node) {
			                    if (node != null) {
			                        setNodeStyle(data);
			                        displayLabelForData(data);
			                    }
			                }
			            });
			            series1.getData().add(data);
			        }
			        bc.getData().add(series1);
				
			}
		});
    }

    /**
     * A simple custom legend for a three valued chart.
     */
    class LevelLegend extends GridPane {

        LevelLegend() {
            setHgap(10);
            setVgap(10);
            addRow(0, createSymbol("-fx-exceeded"), new Label("Exceeded"));
            addRow(1, createSymbol("-fx-achieved"), new Label("Achieved"));
            addRow(2, createSymbol("-fx-not-achieved"), new Label("Not Achieved"));
            addRow(3, button);
            getStyleClass().add("level-legend");
        }

        /**
         * Create a custom symbol for a custom chart legend with the given
         * fillStyle style string.
         */
        private Node createSymbol(String fillStyle) {
            Shape symbol = new Ellipse(10, 5, 10, 5);
            symbol.setStyle("-fx-fill: " + fillStyle);
            symbol.setStroke(Color.BLACK);
            symbol.setStrokeWidth(2);
            return symbol;
        }
    }
    
    

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

Yo i have an issue i post u the errore

Exception in Application start method
java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: Exception in Application start method
at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$154(LauncherImpl.java:182)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NullPointerException
at DynamicallyColoredBarChartWithLabel.start(DynamicallyColoredBarChartWithLabel.java:70)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$161(LauncherImpl.java:863)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$174(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$null$172(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$173(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
... 1 more
Exception running application DynamicallyColoredBarChartWithLabel
C:\Users\mattia tanchis\Documents\NetBeansProjects\JavaFXApplication1\nbproject\build-impl.xml:1340: The following error occurred while executing this line:
C:\Users\mattia tanchis\Documents\NetBeansProjects\JavaFXApplication1\nbproject\build-impl.xml:981: Java returned: 1
BUILD FAILED (total time: 1 second)