You can uninstall or removes an installed libbytecode-java package itself from Ubuntu 12.04 LTS (Precise Pangolin) through the terminal,
$ sudo apt-get remove libbytecode-java
If you would like to remove libbytecode-java and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove libbytecode-java
If you use with purge options to libbytecode-java package all the configuration and dependent packages will be removed.
$ sudo apt-get purge libbytecode-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 libbytecode-java