Persistent (immutable) collection library for Java
High performance bit set implementations.
Collections library of the Staccatissimo project, focused on providing new abstractions that mix object oriented and functional programming style for dealing with iterable objects.
Ponzu is a collections framework for Java. It has JDK-compatible List, Set and Map implementations with a rich API and set of utility classes that work with any JDK compatible Collections, Arrays, Maps or Strings.
Efficient Java collections for primitive integer types
A supplement to the Java Collections library.
Dynamic Collections provides a suite of tools to extend and enhance the Java Collections API.
Guava is a suite of core and expanded libraries that include utility classes, google's collections, io classes, and much much more.
jin collections is a tool libraries that help working with standard Java Collections utility in a "Code by Intenction" way. It is inspired from Smalltalk Collections Utility.