How to install the Vim editor under the LINXU system

My Linux system is Ubantu14.04, the default is the VI compiler, now install the VIM compiler

Open terminal input: sudo apt-get install vim-gtk generally yes, but I have an error message:

Reading Package List ... Completing the dependency tree for the package being analyzed

Reading status information ... There is no available package vim now, but it is referenced by other packages.
This may mean that the missing package may have been discarded,
Or can only be found in other publishing sources

This problem is solved by typing in the terminal: sudo vim/etc/apt/sources.list
Then type it again: sudo apt-get install VIM-GTK.

How to install the Vim editor under the LINXU system