undo the last state change . only possible if there are items in the undo history list . concode_field_sep int cursor concode_elem_sep ArrayList<Memento> mementoStateHistory concode_elem_sep int maxHistorySize concode_field_sep boolean isRedo concode_elem_sep boolean isUndo concode_elem_sep void redo concode_elem_sep void addState
void function ( ) { if ( isUndo ( ) ) { cursor = cursor - 1 ; Memento loc0 = mementoStateHistory . get ( cursor ) ; loc0 . restore ( ) ; } }