[java] Platform.runLater and Task in JavaFX

I have been doing some research on this but I am still VERY confused to say the least.

Can anyone give me a concrete example of when to use Task and when to use Platform.runLater(Runnable);? What exactly is the difference? Is there a golden rule to when to use any of these?

Also correct me if I'm wrong but aren't these two "Objects" a way of creating another thread inside the main thread in a GUI (used for updating the GUI)?

One reason to use an explicite Platform.runLater() could be that you bound a property in the ui to a service (result) property. So if you update the bound service property, you have to do this via runLater():

In UI thread also known as the JavaFX Application thread:

...    
listView.itemsProperty().bind(myListService.resultProperty());
...

in Service implementation (background worker):

...
Platform.runLater(() -> result.add("Element " + finalI));
...

It can now be changed to lambda version

@Override
public void actionPerformed(ActionEvent e) {
    Platform.runLater(() -> {
        try {
            //an event with a button maybe
            System.out.println("button is clicked");
        } catch (IOException | COSVisitorException ex) {
            Exceptions.printStackTrace(ex);
        }
    });
}

• Platform.runLater: If you need to update a GUI component from a non-GUI thread, you can use that to put your update in a queue and it will be handled by the GUI thread as soon as possible.
• Task implements the Worker interface which is used when you need to run a long task outside the GUI thread (to avoid freezing your application) but still need to interact with the GUI at some stage.

If you are familiar with Swing, the former is equivalent to SwingUtilities.invokeLater and the latter to the concept of SwingWorker.

The javadoc of Task gives many examples which should clarify how they can be used. You can also refer to the tutorial on concurrency.