food on railroads of japan

Do they serve cucumber sandwiches on the railroads still?

I'm not sure what you mean by railroad"s". If you're talking about the buffet and restaurant cars on the Shinkansen, they are not in opperation any more.

However, most long-distance trains have venders who, when the train is not overly crowded, goes through all the cars selling bento lunch boxes, drinks, snacks and packs of sandwiches usually including maybe one cucumber sandwich per pack.

Also most railway stations either have a shop inside the station or have a convenience store nearby, and these shops usually sell sandwiches including maybe one cucumber sandwich per pack. Note that sandwiches tend to be sold out right after meal time. Try to go a bit earlier.

...they serve anyone,mate!
Pick up a yummy bento box at the station on the way to your train.

I would advise not buying anything from the food and drink cart on shinkansen. Not only is it very expesnive, it's not usually so good. Just buy from one of MANY bento kiosks in any major station