Java Data Type How to - Create custom DateTimeFormatter

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Question

We would like to know how to create custom DateTimeFormatter.

Answer

import static java.time.temporal.ChronoField.DAY_OF_MONTH;
import static java.time.temporal.ChronoField.MONTH_OF_YEAR;
import static java.time.temporal.ChronoField.YEAR;
// w  ww.ja  v  a  2s. c  o m
import java.time.Instant;
import java.time.LocalDate;
import java.time.Year;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeFormatterBuilder;

public class Main {

  public static void main(String[] args) {
    Instant instant = Instant.parse("2014-07-16T10:15:30.00Z");
    LocalDate localDate = LocalDate.parse("2014-07-16",
        DateTimeFormatter.ofPattern("yyyy-MM-dd"));
    LocalDate localDate2 = LocalDate.parse("2014-07-16",
        DateTimeFormatter.ISO_LOCAL_DATE);

    DateTimeFormatter strangeFormat = new DateTimeFormatterBuilder()
        .appendValue(MONTH_OF_YEAR, 2).appendLiteral("==").appendValue(YEAR, 4)
        .appendLiteral("--").appendValue(DAY_OF_MONTH, 2).toFormatter();

    LocalDate localDate3 = LocalDate.parse("07==2014--16", strangeFormat);

    System.out.println(instant);
    System.out.println(localDate);
    System.out.println(localDate2);
    System.out.println(localDate3);

    LocalDate date = Year.of(2014).atMonth(7).atDay(16);
    String strangeDateFormat = date.format(strangeFormat);

    System.out.println(strangeDateFormat);
  }
}

The code above generates the following result.

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