A presentation I did in IL Java User Group about Java 8, DateTime new features. JSR-310 I wanted it to be informative and a good resource and starting point for this cool feature.

1. Date Time Java 8
(JSR-310)
ilJUG – July 2014
By: Eyal Golan
Tech Lead at eBay

2. A word before starting…
The intent of this presentation is to be
basic source and starting point to the
new Java Date Time API (JSR-310)
2

3. Agenda
• Old vs. New
• JSR 310
• Examples by code
• Resources
3

4. Old Issues
• Date is not a date, nor time. It’s an
instant in time (by epoch)
• Calendar is Date and Time
• Month is 0 (zero) based
• Mutability
4

5. Example – Issues
5

6. Example – Issues
6

7. Example – Issues
7
First try=1274 , second try=0
Use (Calendar)start.clone();

8. Calendar
• YEAR, MONTH,
DAY_OF_MONTH…
• Fields start at 0
• Calendar is mutable
• Methods (set, add…) change the state of
Calendar
8

9. Example – The New Way
9
1274

10. Example – The New Way
10
1274

11. Example – The New Way
11
1274

12. Example – The New Way
12
Today 2014-07-29 and next year 2015-07-29

13. Modeling
• Different date/time scenarios
• Class starts at 12:30
• ilJUG is on 29th July
• The presentation is 1 hour long
• I’ve been working at eBay for 3 years and 6
months
13

14. Example – Issues
14

15. Example – The New Way
15

16. Example – The New Way
16

17. Amount of Time
• How many milliseconds it took
between request to response?
• Set time 10 seconds after now
• Calculate time that passed between
two events
17

18. Example – Old Calculation
18
now Tue Jul 29 01:48:56 IDT 2014 and later Thu Jan 01 04:20:00 IST 1970

19. Example – Old Calculation
19
119 days 6 hours 13 minutes 24 seconds 543 ms
Example taken from stackoverflow

20. Duration and Period
20

21. Duration – Machine Time
21
now 2014-07-28T23:17:40.898Z and later 2014-07-29T01:47:40.898Z
150
2014-07-28T23:17:53.898Z
9000000

22. Period – Human Time
22

24. Guidelines
• Clear
• Fluent
• DSL
• Immutability
• Amount of time, different
representations for different cases
• Human (year, month, day)
• Machine time
24

25. Packages
• java.time
• java.time.chrono
• java.time.format
• java.time.temporal
• java.time.zone
25

26. Some (not all) Classes
• Temporal – Basic interface for DateTime classes
• LocalDate / LocalTime / LocalDateTime …
• Instant
• Start of nanoseconds in timeline. Useful for timestamp
• Clock
• Allowing Temporal creation with alternate clock
• TemporalAmount – Basic interface for classes
that represent amount of time
• Duration
• Period
26

27. Methods Naming Conventions
of Static Creates an instance with validation
to Instance Converts to another type (truncate fields)
at Instance Combines this object with another
(expands)
from Static Converts input parameters to an instance
get Instance Part of the state of the object
27

28. Methods Naming Conventions
is Instance Queries state of an object
with Instance Returns a copy of an object with one
changed element
plus /
minus
instance Returns a copy of an object with amount of
added / subtracted time
parse Static Parses input string to an instance
format Instance Uses formatter to format the object’s values
to produce a string
28

30. Source Code
30
https://github.com/eyalgo/java8-datetime

31. General
31
SystemClock[Asia/Jerusalem]
2014-07-29T05:54:23.337
2014-07-29T08:54:23.338
SystemClock[Asia/Jerusalem]
SystemClock[Europe/Berlin]
2014-7-29

32. General
32
SystemClock[Asia/Jerusalem]
2014-07-29T05:54:23.337
2014-07-29T08:54:23.338
SystemClock[Asia/Jerusalem]
SystemClock[Europe/Berlin]
2014-7-29

33. General
33
SystemClock[Asia/Jerusalem]
2014-07-29T05:54:23.337
2014-07-29T08:54:23.338
SystemClock[Asia/Jerusalem]
SystemClock[Europe/Berlin]
2014-7-29

34. The Basics
34

35. Basic Date and Time
35

36. Partial Dates & Information
36

37. Information, Clear API
37

38. Fluent Operations
38

39. Time Zone
39

40. Using Zone
40

41. Instant
41
From Javadoc:
"This class models a single instantaneous point on the time-line.
This might be used to record event time-stamps in the application...
"...number of seconds that can be held in a long. This is greater than the current
estimated age of the universe...
"...The instant is stored to nanosecond resolution..."

42. Adjusters
• Take Temporal value and adjust it
• Pre defined
• firstDayOfMonth
• firstDayOfYear
• lastInMonth
• Look at TemoralAdjusters
• Custom adjusters
42

43. Adjusters
43

44. Custom Adjusters
44
2014-08-05
2009-09-01

45. Queries – Retrieve Information
45

46. Custom Queries
46

47. Custom Queries
47

48. Parsing and Formatting
• DateTimeFormatter
• Many pre defined formats
• http://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html#predefined
• Immutable
• DateTimeFormatterBuilder
• All classes use the same way
• DateTimeParseException (runtime)
48

49. Parsing and Formatting
49
07**2014--16

50. Legacy Date Time Integration
50

52. 52
https://github.com/eyalgo/java8-datetime
http://docs.oracle.com/javase/tutorial/datetime/iso/index.html
http://docs.oracle.com/javase/tutorial/datetime/index.html
https://jcp.org/en/jsr/detail?id=310
http://www.oracle.com/technetwork/articles/java/jf14-date-time-2125367.html
http://www.mscharhag.com/2014/02/java-8-datetime-api.html
http://geekmonkey.org/articles/24-a-new-date-and-time-api-for-jdk-8
https://today.java.net/pub/a/today/2008/09/18/jsr-310-new-java-date-time-api.html

53. egolan74@gmail.com
https://www.linkedin.com/in/egolan74
http://eyalgo.com/
@eyalgo_egolan