Can I work on Notepad++ if I am using Linux Ubuntu 16.04??

Answer 1

I think Notepad++ only disponible for window's OS...
On linux, you could try SublimeText ( as advanced text editor with syntaxic coloring ) or ( as you seems to target Java ) Eclipse or Intellij ( which are IDE: more than just advanced text editors )

Answer 2

professional developers use IDEs instead of editors to get more functionalities without which your work would be very hard! I suggest you to try NetBeans as first (it smells like beans of coffee).