PART ONE
/File[]<Enter>I<Enter><Esc>kISystem.out.println(f.toString() + "is a directory");<Esc>:wq<Enter>
Here I type /File[]<Enter> and the cursor jumps to the start of /File[].
Here I type I to go into Insert Mode and press <Enter> to create a space for my line.
Here I type <Esc> to exit Insert Mode, going into Normal Mode. Then I press k to move up a line, and I to go back into Insert Mode.
Here I type the command we were told to insert: System.out.println(f.toString() + "is a directory");
I press I to exit Insert Mode.
Then I press :wq<Enter> to write and quit; as you can see from the screenshot, the command has been added to my file.
PART TWO
First style: 147 seconds
Second style: 62 seconds
I forgot to copy paste the appropriate scp command so the first style took me a little longer!
I prefer being already logged into an ssh session (second style) and making the edit in Vim; I think it's a lot more time efficient than copying the file over, logging in, and running it.
If the project requires several lengthy edits, I might choose the first style since I'm not too used to vim yet and writing the edits directly into the file would be quicker for me for now.