Swing GUI Builder Intellij IDEA

I cannot run the form in IntelliJ GUI builder

Exception in thread "main" java.awt.IllegalComponentStateException: contentPane cannot be set to null.

      

        
        
        
      

    

I am assuming that the code to initialize the views is automatically generated. Right now I only have it JPanel

, and somehow it is not auto-initialized, I even thought it was clearly visible on the designer.

This is a Gradle project and I decided to run the generated main function.

What do I need to do to make it work?

public class MyForm {

    private JPanel jPanel;

    public static void main(String[] args) {
        JFrame frame = new JFrame("MyForm");
        frame.setContentPane(new MyForm().jPanel);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
    }
}