How To Access JFrame From Another Class

This is my main.java:

import javax.swing.UnsupportedLookAndFeelException;
public class Main
{
   public static void main(String[] args)
         throws ClassNotFoundException, InstantiationException, IllegalAccessException, UnsupportedLookAndFeelException
   {
      Core window = new Core("GAME1", 0, 0, true, true);
   }
}
 
And this is my Core.java:

import java.awt.GraphicsEnvironment;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

[Code] ....
 
In Core.Java at line 80 how can I access window (

JFrame window = new JFrame(Game_Title); // <- this window
) ?

Also should I use throws or try and catch ?