I will work in a Mod that haves four new bars and they works like the hugry bar, I need the codes of that bar, where I find that class?

and where is FoodStats?

 

Rendering is in GuiIngame, hunger mechanics is in FoodStats.

 

Alright, I understood FoodStats but didn't get much of GuiIngame. Anyways, how do we get started with our own bar?

You can use the RenderGameOverlayEvent to draw new stuff on the HUD. For storing the values I'd use IExtendedEntityProperties.

 

Alright, lets say I subscribe to the RenderGameOverlayEvent.  What do I do next? How do I give it properties like "when to reduce," "when to increase" etc? Can you give me an example?

 

I have never done things like these so please don't mind my nooby questions.

The Gui Overlay tutorial from the wiki is still highly useful, regardless of Minecraft version, though a few minor things (names) have changed since it was written.

 

For IExtendedEntityProperties, either check the Forge wiki tutorial on that subject (can't seem to find it...diesieben's linked it a couple times, I'll change this when I find it) or check mine here. Either one should be plenty to get you started.