Delete all lines that don't contain a string in Sublime Text

Question

So I have around 1000 lines of a text document and was wondering if it's possible to delete all lines on Sublime Text that don't contain a certain keyword, in my case: @

Answer 1

(Edited) Steps

To delete all of the lines NOT containing occurrences of the keyword, use the following:

Mac

• Select your keyword (via double click, drag, etc, say @ in your case)
• Command + Ctrl + G to select all occurrences
• Hold Command and press Left Arrow
• Hold Shift and Command and press Right Arrow
• Cut with Command + X
• Select All with Command + A
• Backspace to delete all file contents
• Paste with Command + V

Windows

• Select your keyword (say @ in your case)
• Alt + F3 to select all occurrences
• Hold Control and press Home
• Hold Shift and press End
• Cut with Ctrl + X
• Select All with Ctrl + A
• Backspace to delete all file contents
• Paste with Ctrl + V