code: public static @Nullable String get(@NotNull Map<String, String[]> requestMap, @NotNull String param) {
      String value = null;
      String[] valueArray = requestMap.get(param);
      if (valueArray != null && valueArray.length > 0) {
        value = valueArray[0];
      }
      // convert encoding to UTF-8 if not form encoding parameter is set
      if (value != null && !hasFormEncodingParam(requestMap)) {
        value = convertISO88591toUTF8(value);
      }
      return value;
    }
docs: Returns a request parameter.<br>
  In addition the method fixes problems with incorrect UTF-8 characters returned by the servlet engine.
  All character data is converted from ISO-8859-1 to UTF-8.
  @param requestMap Request Parameter map.
  @param param Parameter name.
  @return Parameter value or null if it is not set.