Formatting & parsing with DateTimeFormatter

DateTimeFormatter

The DateTimeFormatter class converts between java.time objects and String. It comes in two flavours:

Predefined ISO constants — quick and unambiguous:

LocalDate d = LocalDate.of(2024, 6, 15);
String iso  = d.format(DateTimeFormatter.ISO_LOCAL_DATE);  // "2024-06-15"

ofPattern(...) for locale-style formatting:

DateTimeFormatter fmt = DateTimeFormatter.ofPattern("dd/MM/yyyy");
String text = d.format(fmt);                  // "15/06/2024"
LocalDate back = LocalDate.parse(text, fmt);  // parse it back

Pattern letters (case-sensitive):

When the input string does not match the pattern, parse throws DateTimeParseException — a RuntimeException. You may catch it if parsing user input.