Java8 – Date and Time examples

Java8 – Date and Time examples

This post originally appeared in my blog, www.javabullets.com as part of a series covering Java8 features.

We had two date implementations before Java8 – java.util.Date and java.util.Calendar. There were numerous issues with these implementations which Java8 seeks to resolve with its new java.time API.

Issues

• API Design – java.util.Date and java.util.Calendar both had issues including -
  • months starting from 0
  • in the case of Date year starting from 1900
  • Date also represented a point in time, seconds from the epoch, while its toString method included a TimeZone
  • No single class representing Time or Date
• DateFormat not thread safe

Joda-Time evolved as a defacto standard for Java dates, and its lead developer Stephen Colebourne defined the Java8 JSR-310 API.

Pre-Java8 Date and Calendar Examples

The following snippet demonstrates -

• toString method contains a Timezone
• Date - Month Starts at zero, and year at 1900
• Calendar - Month still starts at zeron, but the year is now fixed

Note this will generate a deprecated API warning

New Features

1. New package – java.time.*
2. Core Classes – LocalDate, LocalTime, LocalDateTime, ZonedDateTime, Period, Duration, Instant
3. Immutable
4. Factory methods

LocalDate And LocalTime Examples

The following snippet demonstrates -

• LocalDate - Date without Timezone
• LocalTime - Time without Timezone

LocalDateTime Examples

• Combines LocalDate and LocalTime
• Called through factory methods of, now, parse
• Immutable
• No TimeZone

ZonedDateTime

• Associate DateTime with TimeZone

CustomAdjuster

• The adjuster will adjust a date according to the defined rule

Period Or Duration

• Period - Duration in day, weeks, month, years
• Duration - days, hours, minutes, seconds

If you have liked this post, check out my personal blog which contains similar tutorials at www.javabullets.com