When using SortedList on a ListView, it can happen that ListView won't update anymore, if the Comparator is poorly implemented. SortedList throws an ArrayIndexOutOfBoundsException.

I've seen this with a more complex Comparator, which returned inconsistent results, e.g. o1 didn't always compare to o2 in the opposite way as the o2 compares to the o1.
Implemeting well-behaved complex comparators is not always easy, so things like this can happen and I wonder if you can protect against it.

(for some reason I didn't even seen any stacktrace in my real app, my ListView just stopped udating itself and I wondered what's up).

Stacktrace:
Exception in thread "JavaFX Application Thread" java.lang.ArrayIndexOutOfBoundsException: -5
at javafx.collections.transformation.SortedList.findPosition(SortedList.java:318)
at javafx.collections.transformation.SortedList.removeFromMapping(SortedList.java:359)
at javafx.collections.transformation.SortedList.addRemove(SortedList.java:389)
at javafx.collections.transformation.SortedList.sourceChanged(SortedList.java:105)
at javafx.collections.transformation.TransformationList.lambda$getListener$16(TransformationList.java:106)
at javafx.collections.transformation.TransformationList$$Lambda$77/10143061.onChanged(Unknown Source)
at javafx.collections.WeakListChangeListener.onChanged(WeakListChangeListener.java:88)
at com.sun.javafx.collections.ListListenerHelper$SingleChange.fireValueChangedEvent(ListListenerHelper.java:164)
at com.sun.javafx.collections.ListListenerHelper.fireValueChangedEvent(ListListenerHelper.java:73)
at javafx.collections.ObservableListBase.fireChange(ObservableListBase.java:233)
at javafx.collections.ListChangeBuilder.commit(ListChangeBuilder.java:482)
at javafx.collections.ListChangeBuilder.endChange(ListChangeBuilder.java:541)
at javafx.collections.ObservableListBase.endChange(ObservableListBase.java:205)
at javafx.collections.ModifiableObservableListBase.remove(ModifiableObservableListBase.java:183)


Sample Code (just click the button a few times). You can also always return 1 from the comparator to trigger it immediately:


import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ListView;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

import java.util.Random;

public class TestApp3 extends Application {
    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(final Stage stage) throws Exception {

        ObservableList<Integer> list = FXCollections.observableArrayList();
        list.addAll(0, 2, 9, 6, 4, 5, 3, 1, 7, 8);

        ListView<Integer> listView = new ListView<>();
        listView.setItems(list.sorted((o1, o2) ->
                // This is the bad comparator.
                // if o1 = 7 and o2 == 8 returns 1
                // if o1 = 8 and o2 == 7 also returns 1
                // This seems to confuse SortedList
                o1 < 5 ? o1.compareTo(o2) : 1));

        Button button = new Button("Click me");
        button.setOnAction(actionEvent -> {
            // Remove the first item from list.
            list.remove(0);
            // Add new random integer between 0 (inclusive) and 10 (exclusive).
            list.add(new Random().nextInt(10));
            System.out.println(list);
        });

        Scene scene = new Scene(new VBox(listView, button));
        stage.setScene(scene);
        stage.show();
    }
}