Why paint(Graphics) is invoked?

Question

I see paint (Graphics g) method in many awt.* codes. In most cases the method is not explicitly called in, anyhow it invokes. In the code below - main() calls constructor Why_Paint() which has no reference to paint(Graphics g)?
import java.awt.*;
import java.awt.event.*;
class Why_Paint extends Frame
     Why_Paint()
          setTitle("Why paint() is invoked? ");
          setSize(270, 160);
          setBackground(Color.cyan);
          addWindowListener(new WindowAdapter()
               public void windowClosing(WindowEvent e)
                    System.exit(0);
          setVisible (true);
     public void paint (Graphics g)
         g.setColor(Color.pink);
          g.fillRect(45, 40, 180, 90);     
     public static void main (String args[])
          new Why_Paint();
}

Answer 1

Thanx for your response.
Thus the automatic paint() method invocation is the cause of blinking screen in many java programs?
I couldn't find any hints/tutorials of customizing automatic invocations (I guess many other methods are called automaticly - main() or init() for example) in my JavaDocs. Can anybody give me an idea of where to look for a link?