Configure applets using Java in NetBeans

import java.awt.*;
import javax.swing.*;
  
public class Practical_39 extends JApplet {
    public void init(){
        setSize(400, 400);
        repaint();
    }
    public void paint(Graphics g){
        g.setColor(Color.red);
        g.drawRect(100, 100, 200, 200);
    }
}