Java SE (Java Platform, Standard Edition)

I'm getting the following exception when trying to update ListView from a different thread (see code below). What am I doing wrong?

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Exception in thread "Thread" java.lang.IllegalStateException: Not on FX application thread; currentThread = Thread
at com.sun.javafx.tk.Toolkit.checkFxUserThread(Toolkit.java:189)
at com.sun.javafx.tk.quantum.QuantumToolkit.checkFxUserThread(QuantumToolkit.java:321)
...
---------

package test;

import java.util.ArrayList;
import java.util.List;
import java.lang.Thread;
import java.util.logging.Level;
import java.util.logging.Logger;

import javafx.application.Application;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.Group;
import javafx.scene.paint.Color;
import javafx.collections.SortedList;
import javafx.collections.ObservableList;

import javafx.collections.FXCollections;
import javafx.scene.control.ListView;
import javafx.scene.control.SelectionMode;

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

    @Override
    public void start(Stage primaryStage) {
        Group root = new Group();
        Scene scene = new Scene(root, 200, 200, Color.BLACK);
        primaryStage.setScene(scene);
        SimpleListView slv = new SimpleListView(root);
        primaryStage.setVisible(true);
        
        UpdateWrapper uw = new UpdateWrapper(slv);
        Thread t = new Thread(uw, "Thread");
        t.start();
    }
}

class SimpleListView{
    ObservableList<String> observedList;
    public SimpleListView(Group parent) {
        final ListView<String> listView = new ListView<String>();
       
        observedList = FXCollections.observableArrayList();
        SortedList<String> sortedList = new SortedList<String>(observedList);
        listView.setItems(sortedList);
        parent.getChildren().add(listView);
        addListElement("From FX thread");
        
    }
    void addListElement(String s){
        observedList.add(s);
    }
}

class UpdateWrapper implements Runnable{
    SimpleListView slv1;
    public UpdateWrapper(SimpleListView slv){     
        slv1 = slv;
    }
    public void run (){
        for (int i = 0; i < 10; i++){
            try {
                Thread.sleep(1000);
            } catch (InterruptedException ex) {
            }
            slv1.addListElement("From other thread : " + i);
        }
    }
}