code: @Nullable
    public static String uppercaseFirstChar(String str, Language language) {
      if (language != null && "nl".equals(language.getShortCode()) && str != null && str.toLowerCase().startsWith("ij")) {
        // hack to fix https://github.com/languagetool-org/languagetool/issues/148
        return "IJ" + str.substring(2);
      } else {
        return changeFirstCharCase(str, true);
      }
    }
docs: Like {@link #uppercaseFirstChar(String)}, but handles a special case for Dutch (IJ in
  e.g. "ijsselmeer" -&gt; "IJsselmeer").
  @param language the language, will be ignored if it's {@code null}
  @since 2.7