Buttons so aparecem quando passo o mouse em cima deles

import java.sql.*;
import java.net.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.lang.*;

public class L extends JFrame 
{
   public L()
   {
     addWindowListener ( new WindowAdapter()
     {
       public void windowClosing ( WindowEvent e )
       {
         System.exit( 0 );
       }
     } );
 
     initComponents();   
   }

   JPanel panePrincipal = new JPanel();
   JPanel paneBotoes    = new JPanel();                   

   private void initComponents()
   {
     Container c = getContentPane();                       
     setTitle ( "L o g i n" );                             
     c.setLayout( null );                                  
     
     c.add ( panePrincipal );                              
     panePrincipal.setBounds ( 1,1,303,20 ); 
     panePrincipal.setBackground ( new Color ( 0,255,153 ) );
     c.add ( paneBotoes );                                 
     paneBotoes.setBackground ( new Color ( 0,255,153 ) ); 
     paneBotoes.setBounds ( 1,166,303,30 );                

     JLabel usuarioLabel;
     JLabel senhaLabel;
     JLabel dataLabel;
     JLabel filialLabel;

     fimButton    = new JButton();
     okButton     = new JButton();

     setDefaultCloseOperation ( WindowConstants.EXIT_ON_CLOSE );
     c.setBackground ( new Color ( 255, 255, 255 ) );
     
     //labels --inicio--
       usuarioLabel = new JLabel ( "Usuario" );
       c.add ( usuarioLabel );
       usuarioLabel.setBounds ( 40, 30, 50, 20 );
 
       senhaLabel = new JLabel ( "Senha" );
       c.add ( senhaLabel );
       senhaLabel.setBounds ( 40, 60, 50, 20 );
    
       dataLabel = new JLabel ( "Data" );
       c.add ( dataLabel );
       dataLabel.setBounds ( 40, 90, 50, 20 );
 
       filialLabel = new JLabel ( "Filial" );
       c.add ( filialLabel );
       filialLabel.setBounds ( 40, 120, 50, 20 );
     //labels --fim--


     //campos editaveis JTextField --inicio--
       usuarioField = new JTextField();
       usuarioField.addActionListener ( new ActionListener() 
       {  public void actionPerformed ( ActionEvent e ) 
          {  
             usuarioFieldActionPerformed( e );
             senhaField.requestFocus();
             senhaField.setVisible(true);
          }
       } );
       c.add ( usuarioField );
       usuarioField.setBounds ( 90, 30, 160, 19 ); 
  
       senhaField = new JPasswordField();
       senhaField.addActionListener ( new ActionListener()
       {  public void actionPerformed ( ActionEvent e )
          {
             senhaFieldActionPerformed( e );
             dataField.requestFocus();
             dataField.setVisible(true);
          }
       } );
       c.add ( senhaField );
       senhaField.setBounds ( 90, 60, 120, 19 );
 
       try
       {  javax.swing.text.MaskFormatter mdataField = new javax.swing.text.MaskFormatter("##/##/####");
          dataField = new javax.swing.JFormattedTextField(mdataField);
       }  catch(Exception e){}
       dataField.addActionListener ( new ActionListener()
       {  public void actionPerformed ( ActionEvent e )
          {
             filialField.requestFocus();
             filialField.setVisible(true);
          }
       } );
       c.add ( dataField );
       dataField.setBounds ( 90, 90, 100, 21 );  

       filialField = new JTextField("01");
       filialField.setColumns(02);
       filialField.addActionListener ( new ActionListener()
       {  public void actionPerformed ( ActionEvent e )
          {
             okButton.requestFocus();
             okButton.setVisible(true);
          }
       } );
       c.add ( filialField );
       filialField.setBounds (90, 120, 20, 19 );
     //campos editaveis JTextField --fim--


     //botoes de confirma e finaliza --inicio--
       okButton.setText ( "Confirma" );
       okButton.setMnemonic ( 'C' );
       okButton.addActionListener ( new ActionListener() {
         public void actionPerformed ( ActionEvent e ) {
           okButtonActionPerformed ( e );
       } } ); 
       c.add ( okButton,  paneBotoes );
       okButton.setBounds ( 33, 170, 100, 23 );

       fimButton.setText ( "Fim" );
       fimButton.setMnemonic ( 'F' );
       fimButton.addActionListener ( new ActionListener() {
         public void actionPerformed ( ActionEvent e ) {
           fimButtonActionPerformed ( e );
       } } );
       c.add ( fimButton, paneBotoes );
       fimButton.setBounds ( 170, 170, 100, 23 );
     //botoes de confirma e finaliza --fim--

     pack();
     setSize( 305, 220 );         //seta o tamanho do frame
     setLocationRelativeTo(null); //posiciona o frame no centro da tela
   } 
 
   private void usuarioFieldActionPerformed ( ActionEvent e )
   {
     if ( usuarioField.equals("") )
     {
        usuarioField.requestFocus();
     }   
   }

   private void senhaFieldActionPerformed ( ActionEvent e )
   {
   }

   private void filialFieldActionPerformed ( ActionEvent e )
   {
   }

   private void okButtonActionPerformed ( ActionEvent e )
   {
     Menu menu = new Menu();
   }
   
   private void fimButtonActionPerformed ( ActionEvent e )
   {
     System.exit( 0 );
   }

   public static void main ( String[] args )
   {
     javax.swing.SwingUtilities.invokeLater ( new Runnable()
     {
       public void run()
       {
          new L().setVisible( true );
       }
     } );
   } 

   private JScrollPane textpane;
   private JTextArea scrollArea;
   private JTextArea output;
   private String url, username, password;
   private Connection connect;

   private JFormattedTextField mdataField;
   private JTextField usuarioField; 
   private JPasswordField senhaField;
   private JTextField filialField;
   private JFormattedTextField dataField;
   private JButton okButton;
   private JButton fimButton;
}

paneBotoes.add(okButton);

c.add ( fimButton, paneBotoes );

paneBotoes.add(fimButton);