import java.util.Arrays;
import java.util.List;
import javafx.application.Application;
import javafx.beans.property.ReadOnlyStringWrapper;
import javafx.beans.property.SimpleStringProperty;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.TreeTableColumn;
import javafx.scene.control.TreeItem;
import javafx.scene.control.TreeTableView;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
 
public class TreeTableViewSample extends Application {
 
    List<Employee> employees = Arrays.<Employee>asList(
        new Employee("Ethan Williams", "ethan.williams@example.com"),
        new Employee("Emma Jones", "emma.jones@example.com"),
        new Employee("Michael Brown", "michael.brown@example.com"),
        new Employee("Anna Black", "anna.black@example.com"),
        new Employee("Rodger York", "roger.york@example.com"),
        new Employee("Susan Collins", "susan.collins@example.com"));

    private final ImageView depIcon = new ImageView (
            new Image(getClass().getResourceAsStream("department.png"))
    );

    final TreeItem<Employee> root = 
        new TreeItem<>(new Employee("Sales Department", ""), depIcon);
    public static void main(String[] args) {
        Application.launch(TreeTableViewSample.class, args);
    }

    @Override
    public void start(Stage stage) {
        root.setExpanded(true);
        employees.stream().forEach((employee) -> {
            root.getChildren().add(new TreeItem<>(employee));
        });
        stage.setTitle("Tree Table View Sample");
        final Scene scene = new Scene(new Group(), 400, 400);
        scene.setFill(Color.LIGHTGRAY);
        Group sceneRoot = (Group) scene.getRoot();

        TreeTableColumn<Employee, String> empColumn = 
            new TreeTableColumn<>("Employee");
        empColumn.setPrefWidth(150);
        empColumn.setCellValueFactory(
            (TreeTableColumn.CellDataFeatures<Employee, String> param) -> 
            new ReadOnlyStringWrapper(param.getValue().getValue().getName())
        );

        TreeTableColumn<Employee, String> emailColumn = 
            new TreeTableColumn<>("Email");
        emailColumn.setPrefWidth(190);
        emailColumn.setCellValueFactory(
            (TreeTableColumn.CellDataFeatures<Employee, String> param) -> 
            new ReadOnlyStringWrapper(param.getValue().getValue().getEmail())
        );

        TreeTableView<Employee> treeTableView = new TreeTableView<>(root);
        treeTableView.getColumns().setAll(empColumn, emailColumn);
        sceneRoot.getChildren().add(treeTableView);
        stage.setScene(scene);
        stage.show();
    }
 
    public class Employee {
 
        private SimpleStringProperty name;
        private SimpleStringProperty email;
        public SimpleStringProperty nameProperty() {
            if (name == null) {
                name = new SimpleStringProperty(this, "name");
            }
            return name;
        }
        public SimpleStringProperty emailProperty() {
            if (email == null) {
                email = new SimpleStringProperty(this, "email");
            }
            return email;
        }
        private Employee(String name, String email) {
            this.name = new SimpleStringProperty(name);
            this.email = new SimpleStringProperty(email);
        }
        public String getName() {
            return name.get();
        }
        public void setName(String fName) {
            name.set(fName);
        }
        public String getEmail() {
            return email.get();
        }
        public void setEmail(String fName) {
            email.set(fName);
        }
    }
}

C:\Users\us\Documents\NetBeansProjects\TreeTableViewSample\dist\run82714293\TreeTableViewSample.jar using platform C:\Program Files\Java\jdk1.8.0_111\jre/bin/java
Exception in Application constructor
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$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: Unable to construct Application instance: class treetableviewsample.TreeTableViewSample
	at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:907)
	at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$155(LauncherImpl.java:182)
	at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
	at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$161(LauncherImpl.java:819)
	at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
	at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
	at java.security.AccessController.doPrivileged(Native Method)
	at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
	at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
	at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
	at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
	... 1 more
Caused by: java.lang.NullPointerException: Input stream must not be null
	at javafx.scene.image.Image.validateInputStream(Image.java:1128)
	at javafx.scene.image.Image.<init>(Image.java:706)
	at treetableviewsample.TreeTableViewSample.<init>(TreeTableViewSample.java:33)
	... 13 more
Exception running application treetableviewsample.TreeTableViewSample