private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
    // TODO add your handling code here:
    try {
        PreparedStatement pst = cn.prepareStatement("UPDATE material SET NOMBRE='"+txtnom.getText()+"',UNIDAD='"+txtuni.getText()+"',PRECIO_U='"+txtpre.getText()+"' WHERE codigo_id=´"+txtcod.getText()+"'");
        pst.executeUpdate();
        mostrardatos("");
    } catch (Exception e){
        System.out.print(e.getMessage());
    }
}