How to keep code from reverting to default?

So I opened the ModEntities.java file for projectiles, and I see all those variables for stuff like velocity updates and tracking range.

However, when I close the tab, even after saving, it undoes all my variables. The strange thing is that when I have the tab open while I run the client, the changes work ingame. It's just when I close the tab, it removes all the changes, even with reformatting and saving multiple times. Why is this happening, how can I make changes to this code without it getting discarded everytime I close it??