Favor Format Over Concatenation

 class​ Mission {
 
  Logbook logbook;
  LocalDate start;
 
 void​ update(String author, String message) {
  LocalDate today = LocalDate.now();
  String month = String.valueOf(today.getMonthValue());
  String formattedMonth = month.length() < 2 ? ​"0"​ + month : month;
» String entry = author.toUpperCase() + ​": ["​ + formattedMonth + ​"-"​ +
  today.getDayOfMonth() + ​"-"​ + today.getYear() + ​"](Day "​ +
  (ChronoUnit.DAYS.between(start, today) + 1) + ​")> "​ +
  message + System.lineSeparator();
  logbook.write(entry);
  }
 }

Understandability and readability don’t just matter in your code—they’re also important for the output your code produces.

If you have to build large strings, you can use format strings ...

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