code: private static Font lookupDefaultDialogFont() {
          Font buttonFont = UIManager.getFont("Button.font");
          return buttonFont != null
                  ? buttonFont
                  : new JButton().getFont();
      }
docs: Looks up and returns the font used by buttons. First, tries to request the button font from
  the UIManager; if this fails a JButton is created and asked for its font.
  
  @return the font used for a standard button