paintComponent(); is not working/ being called

Question

here is my code. and i a little new to coding so please exsplan a lot.

public class main extends JPanel{


    public static Window f = new Window();
        public static int Width = 600;
        public static int Hight = 400;
        public static void main(String args[]){ 

            f.setSize(Width, Hight);
            f.setVisible(true);
            f.setResizable(false);
            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            f.setTitle("FightForYourLife");
            f.setLocationRelativeTo(null);
        }

        public void main(){
            JPanel panel = this;
        }

        public void paintComponent(Graphics g){
            super.paintComponent(g);
            g.setColor(Color.RED);
            g.fillRect(100, 100, 50, 30);
            System.out.println("IT IS PAINTING");
        }



}

Answer 1

Bunch of problems but number 1:

• You never add your main object to your top-level Window, the GUI, and so since it is never added to the GUI, it is never shown nor rendered, and so paintComponent will never be called. Create a new Main object in your public static void main method and add it to your Window (why Window and not JFrame?).

Other issues:

• Your class as a "pseudo" constructor, public void main(){. Remember that constructors don't have return types, not void, not anything. So it should be public main() {.
• Your pseudo constructor does nothing of use. JPanel panel = this; ???
• You will want to follow Java naming rules: class names begin with an upper case letter and fields and methods with a lower case letter. So public class main { should be public class Main {
• Again, why Window and not JFrame?

So for example:

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

// rename main to Main
public class Main extends JPanel{

        public static int WIDTH = 600;
        public static int HEIGHT = 400;

        public static void main(String args[]){ 
            Main main = new Main(); // *** create your main object ***

            JFrame f = new JFrame("FightForYourLife");
            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            f.add(main);  // *** add your main object to the top-level window
            f.pack();  
            f.setResizable(false);
            f.setLocationRelativeTo(null);
            f.setVisible(true);
        }

        public Main(){
            // JPanel panel = this; // this is not helpful, delete it
        }

        @Override // let the JPanel size itself.
        public Dimension getPreferredSize() {
            return new Dimension(WIDTH, HEIGHT);
        }

        @Override  // paintComponent should be protected, not public
        protected void paintComponent(Graphics g){
            super.paintComponent(g);
            g.setColor(Color.RED);
            g.fillRect(100, 100, 50, 30);
            System.out.println("IT IS PAINTING");
        }
}