Thread: main error

I've written code to draw a rectangle. I'm pretty sure i did everything right. This is my code:

package hmm;
 
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
 
public class Hmm {
private static class drawrectangle extends JPanel {
    public void paintComponent(Graphics g) {
    super.paintComponent(g);
            g.drawRect(50, 50, 50, 50);
}
}
 
    public static void main(String[] args) {
      drawrectangle displayPanel = new drawrectangle();
      JPanel content = new JPanel();
      content.add(displayPanel);
      JFrame window = new JFrame();
      window.setContentPane(content);
      window.setVisible(true);
    }
}

However whenever i try to run it i get this error:
"java.lang.NoSuchMethodError: main
Exception in thread "main" Java Result: 1"

I'm don't know what this means. Also, I compiled this code using NetBeans IDE.

I compiled your code and it is working.
restart your IDE
sometimes helps!
give a backgroud color to differ your panels.

What happens if you open a command prompt, change to the folder with the Hmm.class file and enter:
java Hmm

all i needed to was restart the IDE. Thanks