# 920 reference: keyboard shortcuts

The lessons use these keys in Android Studio. Click in the code first. Then the keys go to the
code.

| What it does | Windows and Ubuntu | Mac |
| --- | --- | --- |
| Undo | Ctrl+Z | ⌘Z |
| Redo | Ctrl+Shift+Z | ⌘⇧Z |
| Cut | Ctrl+X | ⌘X |
| Copy | Ctrl+C | ⌘C |
| Paste | Ctrl+V | ⌘V |
| Delete the line | Ctrl+Y | ⌘Delete |
| Duplicate the line | Ctrl+D | ⌘D |
| Comment out the line | Ctrl+/ | ⌘/ |
| Show completions | Ctrl+Space | Control+Space |

- **Delete the line, on Windows:** the first time you press Ctrl+Y, Android Studio asks whether it
  should Redo or Delete Line. Click **Delete Line**.
- **Comment out the line** puts `//` in front of it. Press the same keys again to take it off.
- **Show completions** lists the words that could finish what you typed. When only one fits,
  Android Studio types it for you.