== Get the Previous Selected Objects ==
If user want to know which of the selected objects are new added or removed, they can use the ''getPreviousSelectedObjects'' method to filter out. (only works if model exists)

== Get the Unselected Items ==
If user want to know which of the selected items are deselected, they can use the ''getUnselectedItems'' method to filter out. (if model exists and in paging mold, it should return null)

== Get the Unselected Objects ==
If user want to know which of the selected object are deselected, they can use the ''getUnselectedObjects'' method to filter out. (only works if model exists)

return unselected items in multiple selections mode
return last selected item in single selection mode

Code:

SelectEvent event = new SelectEvnet(/* implement */);
event.getPreviousSelectedItems();
event.getPreviousSelectedObjects();
event.getUnselectedItems();
event.getUnselectedObjects();