You can uninstall or removes an installed libjtharness-java package itself from Ubuntu 16.04 LTS (Xenial Xerus) through the terminal,
$ sudo apt-get remove libjtharness-java
If you would like to remove libjtharness-java and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove libjtharness-java
If you use with purge options to libjtharness-java package all the configuration and dependent packages will be removed.
$ sudo apt-get purge libjtharness-java
If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.
$ sudo apt-get purge --auto-remove libjtharness-java