CsvWriter writer = CsvUtil.getWriter("users.csv", CharsetUtil.CHARSET_UTF_8); writer.writeHeaderLine("ID", "Name", "Email"); writer.writeLine(userList.stream().map(u -> new Object[]{u.getId(), u.getName(), u.getEmail()}).toArray()); writer.close(); The 3.9 version introduced automatic flushing and better character escaping (for commas inside fields). You need to call an external API requiring MD5 signing of a map of parameters. Old way: Sort keys, loop, concatenate strings, handle nulls (15 lines). New way in 3.9:
String sign = SignUtil.md5(paramsMap, "&", "=", "secretKey"); One line. The SignUtil was dramatically improved in 3.9 to handle nested maps and null values gracefully. Deep object graphs ( user.getAddress().getCity().getName() ). Old way: if (user != null && user.getAddress() != null ...) New in 3.9 (using ObjectUtil ): hutool 39 new
If you are still on the Hutool 3.x line, upgrading to is a no-brainer. It offers hundreds of "new" micro-features without disrupting your existing architecture. CsvWriter writer = CsvUtil