According to these lists, Java is #1.
The 2015 Top Ten Programming Languages http://spectrum.ieee.org/computing/software/the-2015-top-ten-programming-languages
Interactive: The Top Programming Languages 2015 http://spectrum.ieee.org/static/interactive-the-top-programming-languages-2015
TIOBE Index for November 2015 http://www.tiobe.com/index.php/content/paperinfo/tpci/index.html

and here, JavaScript is #1.
Languages on GitHub http://githut.info/
The RedMonk Programming Language Rankings: June 2015 http://redmonk.com/sogrady/2015/07/01/language-rankings-6-15/

The devs are using the two most preferred programming languages as NEM's source code.