code: public static String foldCase(String str, boolean defaultmapping) {
          return foldCase(str, defaultmapping ? FOLD_CASE_DEFAULT : FOLD_CASE_EXCLUDE_SPECIAL_I);
      }
docs: <strong>[icu]</strong> The given string is mapped to its case folding equivalent according to
  UnicodeData.txt and CaseFolding.txt; if any character has no case
  folding equivalent, the character itself is returned.
  "Full", multiple-code point case folding mappings are returned here.
  For "simple" single-code point mappings use the API
  foldCase(int ch, boolean defaultmapping).
  @param str            the String to be converted
  @param defaultmapping Indicates whether the default mappings defined in
  CaseFolding.txt are to be used, otherwise the
  mappings for dotted I and dotless i marked with
  'T' in CaseFolding.txt are included.
  @return               the case folding equivalent of the character, if
  any; otherwise the character itself.
  @see                  #foldCase(int, boolean)