public static function categories() { if (empty(self::$categories)) { self::$categories = array("A" => new ABC_Intervall_impl("A", 0.0, 75.0), "B" => new ABC_Intervall_impl("B", 75.0, 95.0), "C" => new ABC_Intervall_impl("C", 95.0, 101.0)); } return self::$categories; }