Eclipse Collections

Eclipse Collections is a collections framework for Java. It has JDK-compatible List, Set and Map implementations with a rich API, additional types not found in the JDK like Bags, Multimaps, and set of utility classes that work with any JDK compatible Collections, Arrays, Maps, or Strings. The iteration protocol was inspired by the Smalltalk collection framework.

Learn Eclipse Collections

Check out the Eclipse Collections Kata, a fun way to help you learn idiomatic Eclipse Collections usage. 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. This particular kata is set up as a series of unit tests which fail. Your task is to make them pass, using Eclipse Collections.

Quick Example

Eclipse Collections puts iteration methods on the container types. Lambdas are simulated using anonymous inner classes. Here's a code example that demonstrates the usual style of programming with Eclipse Collections.

MutableList<Person> people = FastList.newListWith(person1, person2, person3);
MutableList<String> sortedLastNames = people.collect(Person.TO_LAST_NAME).sortThis();
System.out.println("Comma separated, sorted last names: " + sortedLastNames.makeString());

Person.TO_LAST_NAME is defined as a constant Function in the Person class.

public static final Function<Person, String> TO_LAST_NAME = new Function<Person, String>()
{
    public String valueOf(Person person)
    {
        return person.lastName;
    }
};

In Java 8, the Function can be replaced with a lambda:

MutableList<String> sortedLastNames = people.collect(person -> person.getLastName()).sortThis();

Or, a method reference:

MutableList<String> sortedLastNames = people.collect(Person::getLastName).sortThis();

Why Eclipse Collections?

• Improves readability and reduces duplication of iteration code (enforces DRY/OAOO)
• Implements several, high-level iteration patterns (select, reject, collect, inject into, etc.) on "humane" container interfaces which are extensions of the JDK interfaces
• Provides a consistent mechanism for iterating over Collections, Arrays, Maps, and Strings
• Provides replacements for ArrayList, HashSet, and HashMap optimized for performance and memory usage
• Performs more "behind-the-scene" optimizations in utility classes
• Encapsulates a lot of the structural complexity of parallel iteration and lazy evaluation
• Adds new containers including Bag, Interval, Multimap, BiMap, and immutable versions of all types
• Has been under active development since 2005 and is a mature library

License

Eclipse Collections is open sourced under the Eclipse Public License v1.0 and the Eclipse Distribution License v1.0.

How to Contribute

We welcome contributions!

We accept contributions via pull requests here in GitHub. Please see How To Contribute to get started.

Project Roadmap

https://github.com/eclipse/eclipse-collections/wiki/Roadmap

Acquiring Eclipse Collections

Maven

<dependency>
  <groupId>org.eclipse.collections</groupId>
  <artifactId>eclipse-collections-api</artifactId>
  <version>7.1.0</version>
</dependency>

<dependency>
  <groupId>org.eclipse.collections</groupId>
  <artifactId>eclipse-collections</artifactId>
  <version>7.1.0</version>
</dependency>

<dependency>
  <groupId>org.eclipse.collections</groupId>
  <artifactId>eclipse-collections-testutils</artifactId>
  <version>7.1.0</version>
  <scope>test</scope>
</dependency>

<dependency>
  <groupId>org.eclipse.collections</groupId>
  <artifactId>eclipse-collections-forkjoin</artifactId>
  <version>7.1.0</version>
</dependency>

Gradle

compile 'org.eclipse.collections:eclipse-collections-api:7.1.0'
compile 'org.eclipse.collections:eclipse-collections:7.1.0'
testCompile 'org.eclipse.collections:eclipse-collections-testutils:7.1.0'
compile 'org.eclipse.collections:eclipse-collections-forkjoin:7.1.0'

Ivy

<dependency org="org.eclipse.collections" name="eclipse-collections-api" rev="7.1.0" />
<dependency org="org.eclipse.collections" name="eclipse-collections" rev="7.1.0" />
<dependency org="org.eclipse.collections" name="eclipse-collections-testutils" rev="7.1.0" />
<dependency org="org.eclipse.collections" name="eclipse-collections-forkjoin" rev="7.1.0"/>

Additional information

• Project Website: http://www.eclipse.org/collections
• Issues: https://github.com/eclipse/eclipse-collections/issues
• Wiki: https://github.com/eclipse/eclipse-collections/wiki
• StackOverflow: http://stackoverflow.com/questions/tagged/eclipse-collections
• Mailing lists: https://dev.eclipse.org/mailman/listinfo/collections-dev
• Eclipse PMI: https://projects.eclipse.org/projects/technology.collections
• Forum: https://www.eclipse.org/forums/index.php?t=thread&frm_id=329