How to pass Objects from Java App to JavaFX Application

Question

Hello,
New to the JavaFX. I have a Java Swing Application. I am trying to use the TreeViewer in JavaFX since it seems to be a bit better to use and less confusing.
Any help is appreciated.
Thanks
I have my Java app calling my treeviewer JavaFX as
-- Java Application --
public class EPMFrame extends JFrame {
Customer _custObj
private void categoryAction(ActionEvent e)   // method called by Toolbar
        ocsCategoryViewer ocsFX;    //javaFX treeviewer
        ocsFX = new ocsCategoryViewer();    // need to pass in the Customer Object to this Not seeing how to do it.
                                              // tried ocsFX = new ocsCategoryViewer(_custObj) ;    nothing happened even when set this as a string with a value
public class ocsCategoryViewer extends Application {
String _customer;
@Override
    public void start(Stage primaryStage) {
     TreeView <String> ocsTree;
     TreeItem <String> root , subcat;
  TreeItem <String> root = new TreeItem <String> ("/");
        root.setExpanded(true);
         ocsTree = new TreeView <String> (root);
         buildTree();     // this uses the Customer Object.
        StackPane stkp_root = new StackPane();
        stkp_root.getChildren().add(btn);
        stkp_root.getChildren().add(ocsTree);
        Scene scene = new Scene(stkp_root, 300, 250);
        primaryStage.setTitle("Tree Category Viewer");
        primaryStage.setScene(scene);
        primaryStage.show();
    public static void main(String[] args) {
        _customer = args[0];      // temporarily trying to pass in string.
        launch(args);

Answer 1

JavaFX and Swing integration is documented by Oracle - make sure you understand that before doing further development.
What are you really trying to do?  The answer to your question depends on the approach you are taking (which I can't really work out from your question).  You will be doing one of:
1. Run your Swing application and your JavaFX application as different processes and communicate between them.
This is the case if you have both a Swing application with a main which you launch (e.g. java MySwingApp) and JavaFX application which extends application which you launch independently (e.g. java MyJavaFXApp).
You will need to do something like open a client/server network socket between the applications and send the data between them.
2. Run a Swing application with embedded JavaFX components.
So you just run java MySwingApp.
You use a JFXPanel, which is "a component to embed JavaFX content into Swing applications."
3. Run a Java application with embedded Swing components.
So you just run java MyJavaFXApp.
You use a SwingNode, which is "used to embed a Swing content into a JavaFX application".
My recommendation is:
a. Don't use approach number one and have separate apps written in Swing and Java - that would be pretty complicated and unwarranted for almost all applications.
b. Don't mix the two toolkits unless you really need to.  An example of a real need is that you have a huge swing app based upon the NetBeans platform and you want to embed a couple of JavaFX graphs in there.  But if your application is only pretty small (e.g., it took less than a month to write), just choose one toolkit or the other and implement your application entirely in that toolkit.  If your entire application is in Swing and you are just using JavaFX because you think its TreeView is easier to program, don't do that; either learn how to use Swing's tree control and use that or rewrite your entire application in JavaFX.  Reasons for my suggestion are listed here: JavaFX Tip 9: Do Not Mix Swing / JavaFX
c. If you do need to mix the two toolkits, the answer of which approach to use will be obvious.  If you have a huge Swing app and want to embed one or two JavaFX components in it, then use JFXPanel.  If you have a huge JavaFX app and want to embed one or two Swing components in it, use a SwingNode.  Once you do start mixing the two toolkits be very careful about thread processing, which you are almost certain screw up at least during development, no matter how an experienced a developer you are.  Also sharing the data between the Swing and JavaFX components will be trivial as you are now running everything in the same application within the virtual machine and it is all just Java so you can just pass data around as parameters to constructors and method calls, the same way you usually do in a Java program, you can even use static classes and data references to share data but usually a dependency injection framework is better if you are going to do that - personally I'd just stick to simply passing data through method calls.