• What is a Code Kata
  • How does one go about with this kata?
  • Mission
  • Requirements
• Project Structure
• Java Time API
• Solutions to the Katas
• Take Away

Most, if not all Java developers need to rely on Java date and time libraries.

A code-kata is a coding exercise that builds muscle memory by a practice of programming to arrive at a known solution.

The essence of the exercise (presentation material and code kata) is to demonstrate the
usage patterns for dates and times.

This set of code katas rely on fixing broken tests. The tests may have multiple solutions, the intent is to learn and experiment.

The project contains several JUnit tests that fail as org.opentest4j.AssertionFailedError.

Here are simple steps to use this kata:

1. Run the test class(es).
2. One or more tests will fail with the test failure message.
3. Fix the failing tests by taking hints from the TODOs.
4. Repeat above steps until all tests pass.
5. Check the solutions to see if there are other ways to solve. (Remember, the solution may be less performant than yours)
6. Rinse and repeat (delete and checkout again, then back to Step 1) to build muscle memory.

Your mission, should you choose to accept it, will be to fix the JUnit tests. This message will self-destruct in NaN minutes

How to prepare for coding along

This kata is developed as a Java maven project. Ensure that you have:

1. Apache Maven 3.3.x or above. Tested with Apache Maven 3.5.0. Link: https://maven.apache.org/download.cgi

2. JDK 11. Tested with OpenJDK 11 Link: http://jdk.java.net/11/

3. Your favorite Java IDE. IntelliJ IDEA Ultimate was used to develop this kata.

The structure of the project:

|____pom.xml
|____README.md
|
|____src
| |
| |____test                    <------------------- Kata Tests
| | |____java
| |   |____none
| |     |____cvg
| |       |____datetime
| |
| |____main                    <------------------- Shared ErrorMessages & DemoClass
| | |____java
| |   |____none
| |     |____cvg
| |       |____datetime
| |
| |____solutions               <------------------- Solutions 
| | |____java
| |   |____none
| |     |____cvg
| |       |____datetime

The JUnit tests listed below are setup to utilize the Java Time API features.

1. TestKata1InstantAndDateInterop.java

   The tests in this class show interoperability between java.util.Date and the newer java.time.Instant.

2. TestKata2LocalAndZonedDateTimes.java

   The tests in this class show the usage of java.time.LocalDate, java.time.LocalTime, java.time.LocalDateTime and java.time.ZonedDateTime. In addition, this class introduces a java.time.Clock that is extremely handy in writing tests.

3. TestKata3PeriodsAndDurations.java

   The tests in this class show the usage of DateTime ranges: Period, Duration tests.

4. TestKata4DateTimePartials.java

   The tests in this class show the usage of DateTime partials: Month, MonthDay, Year, YearMonth and DayOfWeek tests.

5. TestKata5StreamsInDateTime.java

   The tests in this class show the usage of DateTime in Java stream() lazy iterations.

Solutions for each test:

The key take-away from this kata is a solid understanding of the Java Time API.