The Apache Commons Collections package contains types that extend and augment the Java Collections Framework.

Types that extend and augment the Java Collections Framework.

Brownies Collections complements the Java Collections Framework. GapList combines the strengths of both ArrayList and LinkedList.

The API module of Eclipse Collections, offering rich and efficient data structures for Java.

Java implementation of a concurrent trie hash map from Scala collections library

High Performance Primitive Collections: data structures (maps, sets, lists, stacks, queues) generated for combinations of object and primitive types to conserve JVM memory and speed up execution.

Highly Scalable Java

fastutil extends the Java Collections Framework by providing type-specific maps, sets, lists, and queues with a small memory footprint and fast access and insertion; it provides also big (64-bit) arrays, sets and lists, sorting algorithms, fast, ...

feature-rich collections framework for Java, offering alternatives to standard Java Collections.

The Trove library provides high speed regular and primitive collections for Java.