Question

Why I can not access my variable p in mull class’s iterate method?

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);
    }
    }
}

class MyPanel extends JPanel {
....
}

Why does Eclipse force me to use this:

((MyPanel) p).setParamsRing(i*5, i*7, 200, 200);

instead of:

p.setParamsRing(i*5, i*7, 200, 200);

?

Answer 1

1. Static scopes can only access static variables.
2. You cannot access a local variable declared inside a method from another method unless you pass it as a parameter to the second method or you redeclare it with global visibility.

so what you need is:

public class mull {
    private static final JPanel p;

}

Edit: And to your last question: it’s because p is of type JPanel which doesn’t have any method setParamsRing(). You probably added that method in class MyPanel.