Programming deterministic reactive systems with Synchronous Java

A key issue in the development of reliable embedded software is the proper handling of reactive control-flow, which typically involves concurrency. Java and its thread concept have only limited provisions for implementing deterministic concurrency. Thus, as has been observed in the past, it is challenging to develop concurrent Java programs without any deadlocks or race conditions. To alleviate this situation, the Synchronous Java (SJ) approach presented here adopts the key concepts that have been established in the world of synchronous programming for handling reactive control-flow. Thus SJ not only provides deterministic concurrency, but also different variants of deterministic preemption. Furthermore SJ allows concurrent threads to communicate with Esterel-style signals. As a case study for an embedded system usage, we also report on how the SJ concepts have been ported to the ARM-based Lego Mindstorms NXT system.