TreeViewSample

TreeViewSample.java

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.TreeItem;
import javafx.scene.control.TreeView;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

import java.util.stream.Collectors;
import java.util.stream.IntStream;


public class TreeViewSample extends Application {

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

    @Override
    public void start(Stage stage) {
        TreeItem<String> rootItem = new TreeItem<>("Inbox");
        rootItem.setExpanded(true);
        IntStream.range(0, 6)
                .mapToObj(i -> new TreeItem<>("Message" + i))
                .collect(Collectors.toCollection(rootItem::getChildren));

        TreeItem<String> nested = new TreeItem<>("Nested");
        rootItem.getChildren().get(1).getChildren().add(nested);
        rootItem.getChildren().get(1).setExpanded(true);

        TreeView<String> tree = new TreeView<>(rootItem);
        tree.setShowRoot(false);
        stage.setScene(new Scene(new StackPane(tree), 300, 250));
        stage.show();
    }
}