Duvida Look and feel

import javax.swing.*;  
import java.awt.event.*;  
import java.awt.*;  
  
public class LFDemo extends JFrame{  
        private UIManager.LookAndFeelInfo[] looks =   
UIManager.getInstalledLookAndFeels();  
        
        private JLabel lbLabel01 = new JLabel("Campo1 :");  
        private JTextField jtTexto01 = new JTextField( 10 );  
        private JButton jbLim = new JButton("botao");  
        
        private JRadioButton[] escolha = new JRadioButton[  looks.length ];  
        private ButtonGroup grupo = new ButtonGroup();  
  
  
        public static void main( String[] args ){  
        LFDemo lfd = new LFDemo();  
      lfd.show();  
        }  
  
        public LFDemo(){  
        super("Selecione um Look & Feel");  
        Container c = getContentPane();  
        c.setLayout ( new FlowLayout());  
        c.add(lbLabel01);  
        c.add(jtTexto01);  
        c.add(jbLim);  
        
        ItemSelecionado iselect = new ItemSelecionado();  
        
        for (int i = 0; i < looks.length; i++){  
        escolha[i] = new JRadioButton( looks[i].getName() );  
        escolha[i].addItemListener( iselect );  
        grupo.add( escolha[i] );  
        c.add( escolha[i] );  
        }  
        
        escolha[2].setSelected( true );  
        setDefaultCloseOperation( EXIT_ON_CLOSE );  
        setSize(600,250);  
        }  
  
        public void atualiza(int i){  
          try {  
          UIManager.setLookAndFeel(looks[i].getClassName());  
          SwingUtilities.updateComponentTreeUI(this);  
          }catch(Exception e) {  
          e.printStackTrace();  
          }  
        }  
  
  private class ItemSelecionado implements ItemListener {  
          public void itemStateChanged( ItemEvent e) {  
            for (int i=0; i < escolha.length; i++){  
            if (escolha[i].isSelected())  
              atualiza(i);  
            }  
          }  
  }  
}