To build this todo shortcut functionality(todo live template) from scratch follow the below steps:

1. Go to Settings > Editor > Live Templates
2. Click on '+' icon to add new Live Template
3. Add Abbreviation: todo
   Description: adds //TODO
   Template text: // TODO $date$
4. Click on Edit Variables...
5. Add Name: date
   Expression: date()
   Click OK
6. Cline Define to set Application context
   I just want to use it in Java, so I selected Java
7. Click Apply
8. Click OK

This will set up the shortcut.