C, D (企業B, C, D)を生成 .. return Observable.zip( observableB.map(Optional::of).onErrorReturn(e -> Optional.empty()), observableC.map(Optional::of).onErrorReturn(e -> Optional.empty()), observableD.map(Optional::of).onErrorReturn(e -> Optional.empty()), (optionalResponseB, optionalResponseC, optionalResponseD) -> { .. responseAとoptionalResponseB, C, DからresponseZを生成 .. return responseZ; // チャートのモデル }); });