problem accessing the parent class

[bedeabza]

Hei, I have the following problem within my java application:

I have a Main class that executes when I open the containing .jar file.
In Main I create a new JFrame, then I show it, in the following way: I have a class that extends JFrame, named "Interfata".

Interfata f = new Interfata();
f.setVisible(true);

Then, in Main class I wrote this function

public static void setLook(int tip)

to change the appearance of the application, but I don't know how to access it from f (Interfata object).
Practically, I need to access from a class, one function that resides in the class that instanciated that class.

If anyone has a modality to solve this, I would apreciate it very much.
Thanks!