DateTimeFormatter
- Java course
- Advanced
- Lesson 22/82
- 5 min
Learn formatting with DateTimeFormatter.
Formatting with DateTimeFormatter
DateTimeFormatter turns dates and times into strings and reads them back. You create one with ofPattern by giving a pattern.
Example: DateTimeFormatter f = DateTimeFormatter.ofPattern("dd.MM.yyyy"). Then date.format(f) writes the date as "15.01.2024". The letters in the pattern have fixed meaning: dd day, MM month, yyyy year. To parse back, use LocalDate.parse(string, f).
format and parse
The format method turns a date into a string; parse turns a string into a date. Both take a DateTimeFormatter as a parameter.
Example: String s = date.format(f) and LocalDate d = LocalDate.parse("15.01.2024", f). The pattern must match the shape of the string; otherwise a DateTimeParseException is thrown. When reading user-entered dates it is always safe to use an explicit formatter.
Practice Format a date with dd.MM.yyyy
Create a date with LocalDate.of(2024, 1, 15). Build a formatter with DateTimeFormatter.ofPattern("dd.MM.yyyy"). Turn the date into a string with format and print it with System.out.println.
Starter code
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
// Create Jan 15 2024 with LocalDate.of
// Build a dd.MM.yyyy formatter with ofPattern
// Format and print the resultSample solution
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
public class FormatDate {
public static void main(String[] args) {
LocalDate date = LocalDate.of(2024, 1, 15);
DateTimeFormatter f = DateTimeFormatter.ofPattern("dd.MM.yyyy");
System.out.println(date.format(f));
}
}Expected output
15.01.2024
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Complete the ofPattern call
DateTimeFormatter f = DateTimeFormatter.____("dd.MM.yyyy");DateTimeFormatter f = DateTimeFormatter.ofPattern("dd.MM.yyyy");Explanation: ofPattern creates a formatter from a pattern.
2 Match the DateTimeFormatter methods
| Term | Meaning |
|---|---|
ofPattern |
Creates from pattern |
format |
Turns into string |
parse |
Reads from string |
dd.MM.yyyy |
Pattern |
3 Which method turns a LocalDate into a string?
- of
- format Correct answer
- now
- parse
Explanation: format turns a date into a string with a formatter.