@Override
    public Identifiable checkId(Identifiable item) {
        if (item.getIdentifier() == -1) {
            item.withIdentifier(nextId(item));
        }
        return item;
    }
@ Override public Identifiable checkId ( Identifiable item ) { if ( item . getIdentifier ( ) == - 1 ) { item . withIdentifier ( nextId ( item ) ) ; } return item ; }
set an unique identifier for the item which do not have one set already

@param item
@return