* (thru {@link #addGroupsDataListener}.
*
* <p>Note: you can invoke this method only in an event listener.
*/
protected void fireEvent(int type, int groupIndex, int index0, int index1) {
final GroupsDataEvent evt =
new GroupsDataEvent(this, type, groupIndex, index0, index1);
for (Iterator it = _listeners.iterator(); it.hasNext();)
((GroupsDataListener)it.next()).onChange(evt);
}