RegnumLevelCalculator-setLookAndFeel

import javax.swing.SwingUtilities;
import javax.swing.UIManager;

private void setLookAndFeel() {
  try {
    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
    SwingUtilities.updateComponentTreeUI(this);
    this.pack();
    this.getContentPane().repaint();
  } catch(Exception e){}
}