eating lunch in the train

Is eating lunch or snacks while travelling on the train a proper and accepted etiquette in Japan?

This has been asked and answered many times before.

Basically, it is acceptable on long distance trains, on which all seats are facing forwards. And it is generally not acceptable on commuter trains.

Or another way to put it is, if they serve food on the train you can eat it. If they don't then take that as a no.

So where are you supposed to eat your bento box lunch?

Zavo,

So where are you supposed to eat your bento box lunch?

On long-distance trains - as has already been answered above.

Just like airplanes, long-distance trains usually have a small table attached near your seat, either on the side or the front. In other words, where there is no table to put your food on, food is not appreciated.

But what if I'm not going on a long distance train? In what public places is it acceptable to eat?
I thought bento boxes were very popular in Japan, but I also read that eating in most public places is impolite. These two things just don't seem to match...

Zavo,

In what public places is it acceptable to eat?

In parks.

Bentos are great for those who are on lunch break and want something cheap from the convenience store. However, after buying it they don't eat it outside on the street, unless you're a construction worker. It's better to eat at a table.
Another form of bento is the one a mother makes with all her love in it and gives to her husband and children. Basically it's just a boxed lunch, just like at home.