A code along session to introduce the java.time library in the upcoming release of Java 8. The materials to code along can be cloned from github here: https://github.com/jpgough/JavaTimeLab

1. Java 8 Date Time
By Jim Gough
@JavaJimLondon

2. Agenda
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Adopt a JSR
What exists in Java 7
New Things - The Basics
Working with Date and Time
Parsing and Formatting
Interoperability with java.util.Date
Advanced Queries
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3. Accompanying Materials
• Code along with github project:
• https:/
/github.com/jpgough/JavaTimeLab
!
• More information on my blog:
• http:/
/javajimlondon.blogspot.com/2014/01/
live-coding-on-java-8-date-time-api.html
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4. LJC/JCP
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LJC elected onto the JCP committee
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JCP (Java Community Process)
• The JCP is the mechanism for developing standard
technical specifications for the Java technology
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5. Adopt a JSR
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This is it! JSR-310 is the pilot
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This program is intended to:
– Encourage members of the Java Community to get
involved in a JSR.
– Evangelise that JSR to the wider Java Community
community in order to increase grass roots
participation
– https:/
/java.net/projects/adoptajsr/pages/Home

6. Java Date
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Java Date has been in the language since January 23,
1996
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Many good discussions about what’s wrong with dates
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Mutability
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Date is a DateTime, but there are other classes for SQL
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No Timezones
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Not easy to use
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7. Calendar
• Still mutable
• Can’t format a date directly
• Performing arithmetic operations on
dates not clearly supported. For
example time between two points
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8. Example From It’s High Time
@JavaOne 2008
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How many bugs in this code?
Date date = new Date(2007, 12, 13, 16,
40);
TimeZone zone =
TimeZone.getTimeZone("Asia/HongKong");
Calendar cal = new
GregorianCalendar(date, zone);
DateFormat fm = new
SimpleDateFormat("HH:mm Z");
String str = fm.format(cal);
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9. Example From It’s High Time
@JavaOne 2008
•
6 bugs in the code!
Date date = new Date(2007, 12, 13, 16,
40);
TimeZone zone =
TimeZone.getTimeZone("Asia/Hong_Kong");
Calendar cal = new
GregorianCalendar(date, zone);
DateFormat fm = new
SimpleDateFormat("HH:mm Z");
String str = fm.format(cal);
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10. New Things - The Basics
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New package java.time
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New objects for representing Dates and Time
– LocalDate
– LocalTime
– LocalDateTime
– ZonedDateTime
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11. Working with Date and Time
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Instant - Closest thing to java.util.Date
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Duration
– Measure of time. Eg 34.5 seconds
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Period
– A date based amount of time. Eg 5 days
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Difference important when working with
ZonedDateTime operations.
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12. Java.util.Date
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java.util.Date is actually closest to Instant
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Now has to toInstant method on
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Examples
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13. Parsing and Formatting
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DateTimeFormatter
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Nice predefined formatters:
– DateTimeFormatter.ISO_DATE
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Can build a custom pattern
– Some slight modification to patterns
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.format and .parse conveniently on objects.
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