Eclipse Collections is a comprehensive collections library for Java. The library enables productivity and performance by delivering an expressive and efficient set of APIs and types. The iteration protocol was inspired by the Smalltalk collection framework, and the collections are compatible with the Java Collection Framework types.

The current GA release of Eclipse Collections (11.1.0) is compatible with Java 8+. Eclipse Collections 12.x will be compatible with Java 11+. Eclipse Collections is a part of the OpenJDK Quality Outreach program, and it is validated for different versions of the OpenJDK.

• Productivity
  • Supports eager, lazy, serial and parallel iteration patterns
  • Rich, functional, and fluent APIs with eager methods available directly on collection types
  • Provides List, Set, Bag, Stack, Map, Multimap, BiMap, Interval object container types
  • Readable, Mutable, and Immutable interfaces for each collection type with covariant return types
    • Blog: Rich, Lazy, Mutable, Immutable interfaces in Eclipse collections
  • Mutable and Immutable Collection Factories
    • Blog series: As a matter of Factory
  • Adapters and Utility classes for JCF Types
    • Blog: Iterate over any Iterable in Java
• Performance
  • Memory Efficient Containers
    • Blog: UnifiedMap: How it works?
    • Blog: UnifiedSet - The Memory Saver
  • Optimized Eager, Lazy and Parallel APIs
    • Blog: The unparalleled design of Eclipse Collections
  • Primitive Collections for all primitive types
    • Provides List, Set, Bag, Stack, Map, Interval primitive container types
• Maturity
  • Eclipse Collections has been actively developed and used in financial services applications since 2004
  • Eclipse Collections existed for a decade before concise lambda expressions were added in Java 8
    • Blog: My ten-year quest for concise lambda expressions in Java

• Book: Eclipse Collections Categorically: Level up your programming game
• Blog Series: Getting Started with Eclipse Collections
• Blog Series: The missing Java data structures no one ever told you about
• Blog: Java has Streams. Do we need third-party collections?
• Some Quick Code Examples
• Eclipse Collections Katas, a fun way to help you learn idiomatic Eclipse Collections usage.
  • Start Here - Pet Kata
  • Continue Here - Company Kata
• Eclipse Collections Reference Guide and Javadoc
• Serializing Eclipse Collections with Jackson
• Articles and Blogs
• Some OSS projects that use Eclipse Collections
  • Neo4J, FINOS Legend, Reladomo, Liftwizard, Exchange Core, Dataframe EC, MapDB, Code Browser, Obevo, BNY Mellon Code Katas, Eclipse Nebula NatTable, Eclipse VIATRA, Jackson Datatypes Collections
  • If you work on an open source project that uses Eclipse Collections, let us know!

Note: Eclipse Collections 12.x will be compatible with Java 11+. EC 12.0 has not been released as GA yet, but there are a few milestone releases available to test with.

<dependency>
  <groupId>org.eclipse.collections</groupId>
  <artifactId>eclipse-collections-api</artifactId>
  <version>11.1.0</version>
</dependency>
<dependency>
  <groupId>org.eclipse.collections</groupId>
  <artifactId>eclipse-collections</artifactId>
  <version>11.1.0</version>
</dependency>

implementation 'org.eclipse.collections:eclipse-collections-api:11.1.0'
implementation 'org.eclipse.collections:eclipse-collections:11.1.0'

Eclipse software repository location: https://download.eclipse.org/collections/11.1.0/repository

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

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