Ran the HelloComboBox demo

In the second combo box with option 1, option 2, option 3, option 4 narrator reads as combobox with more than 20 items. But the actual list has only 4 visible items. This will mis-lead an user with only the screen reader.

Looking at the code it looks like
     shortComboBox.setItems(FXCollections.observableArrayList(strings.subList(0, 4)));

 instead of the sublist lenth somewhere whole array list length is getting used.