Challenges in implementing the Real-time Specification for Java']Java (RTSJ) in a commercial real-time Java']Java virtual machine

The increasing complexity of modern real-time systems and the increasing need for real-time behavior in a broad range of applications such as network-centric warfare, telephony and stock trading has encouraged many developers to consider using Real-time Java (TM) for systems previously only written in C Ada or assembly language. The RTSJ standard defines the baseline requirements for a Real-time Java implementation, and commercial Java virtual machine (JVM) implementations include additional features such as real-time garbage collectors and real-time compilation (compiling from Java to native code in a manner compatible with real-time), which make the use of Java practical for these applications. This paper describes some of the challenges that will be faced by implementers of the RTSJ standard based on our experience with implementing IBM's RTSJ-compliant J2SE Java virtual machine, called IBM (R) WebSphere (R) Real-time.