Is there a bar or dining car on the train?

No.

On Japan's Shinkansen trains, refreshments are occasionally offered by Shinkansen staff via a service cart that passes your seat, instead of having a designated dining car.

On the Tokaido and Sanyo Shinkansen (Tokyo <> Osaka, Kyoto, Hiroshima), the service cart only operates for travelers in the Green Cars (first class cars), so you may want to purchase food or drinks at the station before boarding.

On the Hokuriku Shinkansen "KAGAYAKI" and "HAKUTAKA" trains (Kanazawa - Tokyo) a cart sells soft drinks, confectioneries, alcoholic beverages, and snacks on board. No onboard sales are available on "Tsurugi", "Asama" and some "Kagayaki" and "Hakutaka" trains.

Alcoholic and non-alcoholic beverages such as sake and light meals are served free of charge in KAGAYAKI's luxury Gran Class.