getJPanel();

[JunkyFunki]

Salve,

ho difficoltà con il seguente codice:

package primanota;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JLabel;

public class GUIProva  {

    public JLabel tipoOpeL=new JLabel();
    public JPanel panCENTRO=new JPanel();
    
    public GUIProva() {
             
    }

    public void setta() {

        tipoOpeL.setText("Tipo");

    }

    public void vista() {

             javax.swing.GroupLayout layout = new javax.swing.GroupLayout(panCENTRO);
        panCENTRO.setLayout(layout);
        layout.setHorizontalGroup(
                layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addGroup(layout.createSequentialGroup().addContainerGap().addComponent(tipoOpeL).addContainerGap(356, Short.MAX_VALUE)));
        layout.setVerticalGroup(
                layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addGroup(layout.createSequentialGroup().addContainerGap().addComponent(tipoOpeL).addContainerGap(275, Short.MAX_VALUE)));

    }

    public JPanel getJPanel(){
        return panCENTRO;
    }

    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {                
                GUIProva prova = new GUIProva();
                prova.setta();                
                prova.vista();
                
                JFrame pro = new JFrame();                
                pro.add(prova.getJPanel());
                pro.setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
                pro.setTitle("Uno");
                pro.pack();                
                pro.setVisible(true);
                
                
                
                JFrame pro2 = new JFrame();                
                pro2.add(prova.getJPanel());
                pro2.setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
                pro2.setTitle("Due");
                pro2.pack();                         
                pro2.setVisible(true);

            }
        });
    }

   
}

il Jpanel è visibile solo nel secondo Jframe mentre nel primo viene restituito vuoto...come mai?