A minimal extension to Java easing distributed parallel programming of cluster computers. A source code transformation automatically generates a distributed pure Java program based on RMI or KaRMI.

Supports load-time and runtime behavioural reflection in Java by allowing classes to be modified by Java code as they are loaded in. [Freeware, source available]

Supports Design By Contract in Java. Discovers "contracts" during class loading and instruments the class bytecodes on-the-fly to check run-time contract violations. [Apache Open Source Licence]

A framework for load-time transformation of Java programs. [Open Source, LGPL]

Extensible language based on Java. A Metaobject Protocol (MOP) is the extension interface; lets programmers customize language to implement new language features, mechanisms.

Technical paper reviewing PolyJ, an extension to Java allowing parameterized types.

Set of Java packages supporting heterogeneous, concurrent modeling and design. [Open Source, BDL]

A behavioral interface specification language that can be used to specify the behavior of Java modules.