Java ZonedDateTime

Posted by On 7月 06, 2016 0 Comment

New Date

From Java 8, there are additional Date management class.
In the past, Date related class for Java are following

  • Date
  • Calendar

From Java 8, several classes are added, these are some of them.

  • ZonedDateTime
  • LocalDateTime
  • LocalDate
  • LocalTime

What is difference between Zonedxxx and Localxxxx.
Zonedxxx has Zone data, date can change using ZoneId.
Localxxx is only local date. It doesn’t have Zone idea and other timezone date.

I introduce the usage of this. This entry is first for them.

ZonedDateTime

ZonedDateTime has timezone idea.
By default, timezone is system.

System Zone and Zone set

UTC

ZonedDateTime utc = ZonedDateTime.now(ZoneOffset.UTC);
System.out.println(utc);

zoneId zoneIdUTC = ZoneId.of("UTC");

ZoneId zoneId = ZoneId.of("Asia/Tokyo");
ZonedDateTime jst = ZonedDateTime.ofInstant(utc.toInstant() , zoneId ); // Convert JST

Style

ZonedDateTime gmt = ZonedDateTime.parse("2016-07-06T09:30:40Z[GMT]");
ZonedDateTime sing = ZonedDateTime.parse("2016-07-04T12:30:40+01:00[GMT+08:00]");
System.out.println(gmt);		// 2016-07-06T09:30:40Z[GMT]
System.out.println(sing);		// 2016-07-04T12:30:40+08:00[GMT+08:00]

Convert other class

// Date
ZonedDateTime utc = ZonedDateTime.now(ZoneOffset.UTC);
Date date = Date.from(utc.toInstant());
System.out.println(date);

ZonedDateTime today = ZonedDateTime.now();
System.out.println("ZonedDateTime " + today);
System.out.println("LocalDate " + today.toLocalDate());
System.out.println("LocalDateTime " + today.toLocalDateTime());
System.out.println("LocalTime " + today.toLocalTime());

Get Data and Calculation

ZonedDateTime today = ZonedDateTime.now();
System.out.println("Year:" + today.getDayOfYear());
System.out.println("Month:" + today.getMonth());
System.out.println("Day:" + today.getDayOfMonth());
		
ZonedDateTime firstDayofMonth = today.withDayOfMonth(1);
System.out.println(firstDayofMonth);

Calculation

This sample is to calculate flight time.

// Start from Singapore(Changi) 2016/07/07 10:00 am
ZonedDateTime start = ZonedDateTime.of(2016, 7, 7, 10, 0, 0, 0, ZoneId.of("Asia/Singapore"));

// Flight is 6 hour 30 minutes to Japan(Haneda)
ZonedDateTime arrive = start.plusHours(6).plusMinutes(30).withZoneSameInstant(ZoneId.of("Asia/Tokyo"));
System.out.println(arrive);

Next entry, I want to explain about dateformat

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