JOptionPane.showConfirmDialog: Tabbing between options creates wrong result

Question

In JOptionPane.showConfirmDialog, when pressing <tab> to move between options and then pressing <Enter> I always get a returned zero (0) no matter which button is in focus. Is this a (known) bug or am I stupid?
I run the following code.
import javax.swing.*;
public class TabOptions
public static void main (String [] args)
     int n = JOptionPane.showConfirmDialog (null, "Use <Tab> to shift option-button, then press <Enter>. " +
                         "I'll write the returned value to sdt out.");
     System.out.println ("Returned value: " + n);
}

Answer 1

import javax.swing.*;
class TabOptions
public static void main (String [] args)
UIManager.put("Button.defaultButtonFollowsFocus", Boolean.TRUE);//<--------------------
int n = JOptionPane.showConfirmDialog (null, "Use <Tab> to shift option-button, then press <Enter>. " +
"I'll write the returned value to sdt out.");
System.out.println ("Returned value: " + n);
}