$ sudo apt-get update
$ sudo apt-get install icedtea-netx 

icedtea-netx is installed in your system.

Make ensure the icedtea-netx package were installed using the commands given below,

$ sudo dpkg-query -l | grep icedtea-netx *

You will get with icedtea-netx package name, version, architecture and description in a table

icedtea-netx package basic information: