buttonBackground = null; buttonShadow = null; buttonDarkShadow = null; buttonHighlight = null;
LookAndFeel.uninstallBorder(comboBox);
  protected void uninstallDefaults()  {    if (comboBox.getFont() instanceof UIResource)      comboBox.setFont(null);    if (comboBox.getForeground() instanceof UIResource)      comboBox.setForeground(null);        if (comboBox.getBackground() instanceof UIResource)      comboBox.setBackground(null);    buttonBackground = null;    buttonShadow = null;    buttonDarkShadow = null;    buttonHighlight = null;  }