Why I can noy access my variable p in mull form iterate method? How to resolve a problem? Hot to set class variable to be visible to its public static methods?

public class mull {
    public static void main(String[] args) throws InterruptedException  {
    final JPanel p = createAndShowGUI();

        Timer timer = new Timer(1000, new MyTimerActionListener());

    timer.start();
    try {
      Thread.sleep(10000);
    } catch (InterruptedException e) {
    }
    timer.stop();
public static void iterate(){

    for (int i  = 0; i < 55; i++){
         // "p cannot be resolved"
    p.moveSquare(i*10, i*10);
        p.setParamsRing(i*5, i*7, 200, 200);
//            p.repaint();
        }
    }
}

class MyPanel extends JPanel {
....

}

How to access variable set in another method (in this example main())?

Why Eclipse forces me to use this ((MyPanel) p).setParamsRing(i*5, i*7, 200, 200); instead of this p.setParamsRing(i*5, i*7, 200, 200);?