Why the paint() method is called two times ?

This code calls two times the paint() method when I run this:

package KLL;
import javax.swing.*;
import java.awt.*;


public class KLL extends JFrame {

static int a;
static int b;
public KLL(){
super();
a=12;
b=20;

setSize(300,300);

setVisible(true);

}

public void paint(Graphics g){

System.out.println(a);
Graphics2D g2;
g2=(Graphics2D) g;
g2.draw3DRect(100, 100, a, b, false);
}

public static void main (String[] args) throws InterruptedException{
KLL K=new KLL();
Thread.currentThread();
Thread.sleep(3000);
a=80;
b=120;
K.repaint();
Thread.sleep(3000);
a=200;
b=120;
K.repaint();
}

}

When using repaint() it is called only 1 time which is understandable. But why when I run this code it is called two times at the beginning ??

I have no idea but that is NOT the way to do custom painting.

Read the section from the Swing tutorial on Custom Painting for the proper way to do this.

Thank you for the answer and the link.

However it is very strange why this behavior is followed in that code....

The JVM AWT engine determines how and when to call paint(); It can merge repaint() requests into a single call to paint().

Bottom-line Not always easy to predict when paint() will be called.

Hm... Thank you.

Interesting...