code: public static String inputStreamToString(InputStream is) throws MPException {
          String value = "";
          if (is != null) {
              try {
                  ByteArrayOutputStream result = new ByteArrayOutputStream();
                  byte[] buffer = new byte[1024];
                  int length;
                  while ((length = is.read(buffer)) != -1) {
                      result.write(buffer, 0, length);
                  }
                  value = result.toString("UTF-8");
  
              } catch (Exception ex) {
                  throw new com.mercadopago.exceptions.MPException(ex);
              }
          }
          return value;
  
      }
docs: Static method that transform an Input Stream to a String object, returns an empty string if InputStream is null.
  
  @param is                    Input Stream to process
  @return                      a String with the stream content
  @throws MPException