Thank you for your valuable reply based on latest version of Java, Abhay!
It works, but found limitation as it seems that file extension is analyzed. So if you change extension it will display type based on extension, no matter what file's content is.
Have found Apache Tika
It works based on content, no matter what extension is.
What will examine further, is how to distinguish .csv, pipe-delimited, TAB delimited content on the most elegant way as they're all recognized as text/plain
. Opening them and parsing, is an option
Thanks for you critics Jeff, will try to do more accurate research. If you find topic low-level post solution or ignore it please. There might be others who are interested, so I'd expand it further