$ sudo apt-get update
$ sudo apt-get install libnekohtml-java 

libnekohtml-java is installed in your system.

Make ensure the libnekohtml-java package were installed using the commands given below,

$ sudo dpkg-query -l | grep libnekohtml-java *

You will get with libnekohtml-java package name, version, architecture and description in a table

libnekohtml-java package basic information: