Java Date and Time - Past and Future

JavaDate and Time

Past and Future

Iulian DogariuNess Technologies

Iași Java User Group1379518200000

APIs that make me happy

Timestamp

“System.currentTimeMillis() should be enough for anybody”

-- Bill Gates,after seeing the JDK 1.0 Javadocs

(well, not really)

java.util.Date

java.util.Calendar

POLA !

java.util.Calendar, as of JDK 7

• Missing abstractions• Full of bad surprises– Unsound design – violates Liskov– Violates POLA– Getter methods with side effects!– Not thread safe– Untestable

Instants

Instants

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2013-09-18T15:31:14Z

2013-09-18T18:30+03:00

2013-09-18T18:31:14+03:00

Civil time

Instants ↔ Civil time

Let’s Practice !

Java 8 Time vs Joda Time

We love .NET too

http://nodatime.org/

Java 8 Time – Recap

• Instants• Civil time (Days, Months, Weeks)• Zones and Offsets

• Choose your abstractions well, and the rest is simple

Instants

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java.time.Instantjava.time.ZonedDateTimejava.time.OffsetDateTime

java.tim

e.Durati

on

Civil time java.time.LocalDateTime

java.time.Period

Q, and, hopefully, A

?

Links• Java 8 EA https://jdk8.java.net/download.html

– Current version: b106

• Javadocs: http://download.java.net/jdk8/docs/api/

• ISO 8601: http://en.wikipedia.org/wiki/ISO_8601

• Olson TZ aka Zoneinfo – http://www.iana.org/time-zones– http://en.wikipedia.org/wiki/Tz_database

• Stephen Colebourne - author of Joda Time

Thank you!