public static void SoloLetras(java.awt.event.KeyEvent evt,javax.swing.JTextField txt){
      char caract;
        // Convierte TODO ingreso a mayusculas
        String letra = (evt.getKeyChar() + "").toUpperCase();
        evt.setKeyChar(letra.charAt(0));
        caract = evt.getKeyChar();

        if(!(caract >= 'A' && caract <= 'Z')&& (caract != ' ')){
                    evt.consume();}
        if(txt.getText().length()>20)
            evt.consume();
    }