How to actually lock the code?

So just wondering how do you exacly lock the code in the .java classes so that MCreator does not regenerate it? I could not find any explanation on how to and right clicking on the Workspace file browser (not the system file browser) does not show me the option to lock the code.

Anyone knows how to do that? For example the one I was trying to lock was in the Source net/mcreator/purchaos (purechaos is the mod name, so that is why the directory is called like that) /init/PurechaosModEntityRenderers.java