Collections Kata
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Eclipse Collections Kata

A kata is an exercise in martial arts. A code kata is an exercise in programming which helps hone your skills through practice and repetition. The Eclipse Collections Kata is a fun way to help you learn idiomatic Eclipse Collections usage. This particular kata is set up as a series of unit tests which fail. Your task is to make them pass, using Eclipse Collections.

Initialize Kata

Clone this repo or simply download and extract the master zip file, then follow the instructions below for your IDE/platform.

Eclipse users

Initialize Eclipse project with the command below.

./gradlew eclipse
gradlew.bat eclipse

Once the project is initialized, you can import the project from "Import" => "General" => "Existing Projects into Workspace". Select "eclipse-collections-kata" directory as root directory, make sure to choose "Search for nested projects" option and finish.

IntelliJ IDEA users

Initialize IntelliJ IDEA project with the command below.

./gradlew idea
gradlew.bat idea

Once the project is initialized, you can open the project from "File" => "Open..." => choose "eclipse-collections-kata" folder. You might see a dialog to suggest importing Gradle project, it's up to you to do so if you'd like to invoke gradle builds from IDEA. Kata can run in IDEA even if you don't import Gradle project.

NetBeans users


open as a Maven project

You can open the project directly from "File" => "Open Project..." => choose "eclipse-collections-kata" folder. In the "Open Project" dialog you might select the option "Open Required Projects" to automatically open the two modules.

open as a Gradle project

The "Gradle Support" plugin needs already to be installed.
Temporarily remove/rename the pom.xml file. Then open the project from "File" => "Open Project..." => choose "eclipse-collections-kata" folder.
Restore the pom.xml file.

Work on Kata exercises

There are two separate katas under different directories (Company Kata and Pet Kata).


To get started, you can refer to slides for the Instruction and Pet Kata to learn how to set-up Kata, basic features of Eclipse Collections corresponding to each Pet Kata exercise and then solutions.

To learn wider range of functionalities, slides for Company Kata are now available online as well.

Check out the solution branch for your reference.

Enjoy happy learning with Eclipse Collections Kata!

Reference Guide

The Eclipse Collections Reference Guide is a great way to get an overview of the extensive features available in the framework.


The API Design of Eclipse Collections covers the design decisions that went into making Eclipse Collections and guiding its evolution from Java 4 through Java 9. The content of the presentation is also available in a convenient to read markdown format.