How turn on Emojis in 2017.1 ?

What do you mean by "turn on"? What OS do you use?

Windows 7

Such comment in Java class dont works:

// :)

IDEA only supports Emoji Unicode characters (https://en.wikipedia.org/wiki/Emoji), not common abbreviations for emoji.

Thx, it works.

How to turn them off in code?? 

You cannot turn them off - IDE just renders Unicode characters present in the file. You can probably replace them by escape sequences accepted by your programming language.