Vim Usage: remove all empty lines

In text editing, especially when you copied the content from some website, you might want to delete all empty lines in your text. In the past, I will do something stupid which is to delete the empty line one by one. It takes time and I use this command to achieve my goal
dd, (go to next empty line), then "." ,until you delete all the empty line.

Explanation:

• dd - delete whole line
• . - repeat the last command (I like this one, very useful)

However, I realized there is a command which is much more useful and handy:

:g/^$/d

Feel free to use it if you need to delete all empty lines :-)