$ sudo apt-get remove java6-sdk

Uninstall java6-sdk including dependent package

If you would like to remove java6-sdk and it's dependent packages which are no longer needed from Ubuntu,

$ sudo apt-get remove --auto-remove java6-sdk

Use Purging java6-sdk

If you use with purge options to java6-sdk package all the configuration and dependent packages will be removed.

$ sudo apt-get purge java6-sdk

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 java6-sdk

See Also,