String (String s) { assert !s.isEmpty(); String result = WIN_BACKSLASHES_PRECEDING_QUOTE.matcher(s) .replaceAll("$1$1") // duplicate trailing backslashes and those preceding a double quote .replace("\"", "\\\""); // backslash-escape all double quotes if (!result.equals(s) || WIN_QUOTE_SPECIAL.matcher(s).find()) { result = quote(result, Q); } return result; }