Problema JDesktopPane [Resolvido]

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.beans.PropertyVetoException;

import javax.swing.JDesktopPane;
import javax.swing.JFrame;
import javax.swing.JInternalFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;

public class JInternalFrameExemple extends JFrame implements ActionListener {

private static final long serialVersionUID = 1l;

final JDesktopPane desktop = new JDesktopPane();

private JMenu menu = new JMenu( "menu" );

private JMenuItem menuItem = new JMenuItem( "InternalFrame 1" );

private JMenuItem menuItem2 = new JMenuItem( "InternalFrame 2" );


public JInternalFrameExemple() {

super( "JInternalFrame Exemple" );

setSize( 500, 400 );
setLocationRelativeTo( this );
setDefaultCloseOperation( JFrame.DISPOSE_ON_CLOSE );

getContentPane().add( desktop );

JMenuBar menuBar = new JMenuBar();
setJMenuBar( menuBar );

menuBar.add( menu );
menu.add( menuItem );
menu.add( menuItem2 );

menuItem.addActionListener( this );
menuItem2.addActionListener( this );

setVisible( true );

}

public void actionPerformed( ActionEvent e ) {

if ( e.getSource() == menuItem ) {
addTela( new JInternalFrame( "Janela 1" ) );
}
if ( e.getSource() == menuItem2 ) {
addTela( new JInternalFrame( "Janela 2" ) );
}

}

private void addTela( JInternalFrame arg ) {

if ( !temTela( arg ) ) {

desktop.add( arg );
arg.setVisible( true );

}

}

private boolean temTela( JInternalFrame arg ) {

JInternalFrame[] telas = desktop.getAllFrames();

for ( int i = 0; i < telas.length; i++ )
if ( telas[ i ].getTitle().equals( arg.getTitle() ) )
return true;

return false;

}
public static void main( String[] args ) {


new JInternalFrameExemple();
}

}