Exploring JSR310 - prep for coding

Where to get the code - prep for coding

The HG source repo in OpenJDK is here :hg clone http://hg.openjdk.java.net/threeten/threeten/jdk
or you can just :
run > hg clone http://hg.openjdk.java.net/threeten/threeten/jdk threetenjdk
(beware this is the entire JDK, big)

Or just download the latest OpenJDK 8

http://jdk8.java.net/download.html

Project home

Project home is : http://openjdk.java.net/projects/threeten/

Mailing list

 The mailing list for the project is here : https://lists.sourceforge.net/lists/listinfo/threeten-develop

 Getting it built

The project is built with Apache Ant.
run >ant

At the time of writing it produced one JAR
build/threeten-0.7.0-alpha.jar

Java docs

Java docs are hosted on the OpenJDK site : http://cr.openjdk.java.net/~rriggs/threeten-javadoc/index.html

JSR 310 Use Cases

It's alway nice to see that a piece of software has use cases attached.

Installing artifact into Maven

>mvn install:install-file -Dfile=threeten-0.7.0-alpha.jar -DgroupId=javax     -DartifactId=time -Dversion=0.7.0-alpha -Dpackaging=jar

In my next blog

I will publish some source code of the issues addressed in JSR310 compared to the current Date and Time API.
I will do this via JUnit4

A new Date and Time API for Java 8

Why is a new Date and Time API needed for Java ?

This series of blogs is apart of the JoziJUG Adopt a JSR


Have a look at the following code as illustrated this document.

    Date date = new Date(2007, 12, 13, 16, 40);//Issue 1 and Issue 2
    TimeZone zone = TimeZone.getInstance("Asia/HongKong");//Issue 3
    Calendar cal = new GregorianCalendar(date, zone);//Issue 4
    DateFormat fm = new SimpleDateFormat("HH:mm Z");
    String str = fm.format(cal); //Issue 5

Issue 1 

The year should not be 2007, it should be 2007 - 1900. i.e. The year starts with 1900

Issue 2 

Months start with 0. So 0 is January , 11 is December and 12 is invalid.

Issue 3 

Asia/HongKong is a ISO standard timezone. But the API expects an underscore in the timezone name. e.g. Asia/Hong_Kong

Issue 4 

The constructor to GregorianCalendar or even method Calendar.getInstance(date) does not exist. A calendar needs to be created and then set.

Issue 5 

A SimpleDateFormat can not format a Calendar, the Calendar needs to be converted to a Date first

What about Joda Time ? 

Joda time is a widely used alternative to the standard Java Date and Time API but according to author it has flaws and can not just be included in the core Java.

In the next blog 

 I will discuss Joda time as we prepare to explore the already written JSR 310 code.