code: @Nonnegative
    public static int getOccurrenceCountIgnoreCase (@Nullable final String sText,
                                                    final char cSearch,
                                                    @Nonnull final Locale aSortLocale)
    {
      return sText != null ? getOccurrenceCount (sText.toLowerCase (aSortLocale), Character.toLowerCase (cSearch)) : 0;
    }
docs: Count the number of occurrences of cSearch within sText ignoring case.
  
  @param sText
  The text to search in. May be <code>null</code>.
  @param cSearch
  The character to search for.
  @param aSortLocale
  The locale to be used for case unifying.
  @return A non-negative number of occurrences.