The Well Grounded Java 7 Developer

Hi all,

I’ve obviously not posted for quite some time and here is the reason why…..

It’s been a long time coming, but I’m very happy to announce that Ben Evans and I have been contracted to write “The Well  Grounded Java 7 Developer” for Manning publications.  We’ve been spending the last month frantically getting the first few chapters out and a whole host of other book related activities, but now that I’m in full chapter writing mode I’ll be adding regular posts to this blog.

A majority of my future posts will focus on interesting areas in this book and firstly I’d like to show a reworked extract from the new Date and Time API section.

Modeling Date and Time

The new API models time as a sequence of consecutive instants separated by fixed durations[1].  Java 7 maps these concepts directly on to classes, here’s a more detailed explanation:

• The javax.time.Instant class represents a specific point on a discrete time-line e.g. January 23rd, 1996 at 09:00:00,0 UTC, the day that Java 1.0 was released.

• The javax.time.Duration class represents a section of elapsed time in nanoseconds, e.g. The 400 nanoseconds it takes for a PIC12C672-04 Microchip to execute an instruction set.

So as you can imagine, any point of time can be modeled by simply applying a Duration (positive or negative) to a starting Instant.

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Calendering

With regards to calendaring, the main Calendar is ISOChronology, but other calendars such as CopticChronology and ThaiBuddhistChronology are supported.  The Chronology interface can be extended from to provide other implementations.

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Timezone support

Timezone support is also provided via three core classes:

• LocalDateTime – Represents date/time without an offset or a time zone.

• OffsetDateTime – Represents date/time with an offset but not time zone.

• ZonedDateTime – Represents date/time with an offset and a time zone.

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[1]               This phrase is almost 100% uplifted from an excellent early primer article by Jesse Farnham, see  http://today.java.net/pub/a/today/2008/09/18/jsr-310-new-java-date-time-… for details

The book will be loaded with more in depth explanations and of course plenty of code samples.  If you’re interested in becoming a reviewer then please let me know!