private boolean camposNecesarios () {
        if ((jTextField1.getText().length()==0) ||
            (jTextField2.getText().length()==0) ||
            (jTextField3.getText().length()==0) ||
            (jTextField4.getText().length()==0) ||
            (jTextField5.getText().length()==0) ||
            (jTextField6.getText().length()==0))
        {
            JOptionPane.showMessageDialog(null, "Complete todos los campos!","Atención",JOptionPane.WARNING_MESSAGE);
            return false;
        }
        return true;        
    }