The serializable class FMFrame does not declare a static final serialVersionUID field of type long

Hallo,
warum bekomme ich diese Warnung?
"The serializable class FMFrame does not declare a static final serialVersionUID field of type long"
Mein Code dazu:

Code (Java):

package GUI;
import javax.swing.*;

public class FMFrame extends JFrame{
   
    public FMFrame(){
        this.setTitle("Meine GUI");
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(500, 500);
        this.setLocationRelativeTo(null); // Fenster ist in der Mitte des Desktops.
    }

}
 

The serializable class FMFrame does not declare a static final serialVersionUID field of type long