$ sudo apt-get update
$ sudo apt-get install javahelp2 

javahelp2 is installed in your system.

Make ensure the javahelp2 package were installed using the commands given below,

$ sudo dpkg-query -l | grep javahelp2 *

You will get with javahelp2 package name, version, architecture and description in a table

javahelp2 package basic information: