[1.7.10] Making a Modded Item using more then one class

I'll go straight to the point, I'm using a class that holds all my items but because of that I can't use super.onEaten in the Mod Item class because it'll mess up the code, so because of this, I'm trying to add something to the public static Item "Whatever" but doesn't work or can't find out how, my goal is to add a part of code that fetches more things about the item but without adding a entire chuck of code somewhere else and can't find it. Basically having a storage of the basic code then uses another class to add more to it. Sorry if it's confusing but I'm out of ideas and I tried everywhere.