On implementing high level concurrency in Java']Java

Increasingly threading has become an important architectural component of programming languages to support parallel programming.. Previously we have proposed an elegant language extension to express concurrency and synchronization. This language called Join Java has all the expressiveness of Object Oriented languages whilst offering the added benefit of superior synchronization and concurrency semantics. Join Java incorporates asynchronous method calls and message passing. Synchronisation is expressed by a conjunction of method calls that execute associated code only when all parts of the condition are satisfied. A prototype of the Join Java language extension has been implemented using a fully functional Java compiler allowing us to illustrate how the extension preserves Join semantics within the Java language. This paper reviews the issues surrounding the addition of Join calculus constructs to an Object Oriented language and our implementation with Java. We describe how, whilst the Join calculus is non-deterministic, a form of determinism can and should be specified in Join Java. We explain the need for a sophisticated yet fast pattern matcher to be present to support the Join Java compiler. We also give reasons why inheritance of Join patterns is restricted in our initial implementation.