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The Real Time Specification for Java (RTSJ) is an augmentation of Java for real time applications of various degrees of hardness. The central features of RTSJ are real time threads; user defined schedulers; asynchronous events, handlers, and control transfers; a priority inheritance based default scheduler; non-heap memory areas such as immortal and scoped, and non-heap real time threads whose execution is not impeded by garbage collection. The Robust Software Systems group at NASA Ames Research Center has Java PathFinder (JPF) under development, a Java model checker. JPF at its core is a state exploring JVM which can examine alternative paths in a Java program (e.g., via backtracking) by trying all nondeterministic choices, including thread scheduling order. This paper describes our implementation of an RTSJ profile (subset) in JPF, including requirements, design decisions, and current implementation status. Two examples are analyzed: jobs on a multiprogramming operating system, and a complex resource contention example involving autonomous vehicles crossing an intersection. The utility of JPF in finding logic and timing errors is illustrated, and the remaining challenges in supporting all of RTSJ are assessed.

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This paper presents our work on model checking distributed applications. We refer to distributed applications as a collection of communicating processes, regardless of their physical locations and the communication means. Our work targets applications written in Java. It relies on the multiprocess support included in Java Pathfinder (JPF) version 7 which allow for verifying the bytecode of distributed applications. The basic support for distributed applications in JPF does not account for communication between processes. In this work, we address this limitation. The work is implemented as a JPF extension which models inter- process communication (IPC) mechanisms. It uses a form of partial order reduction (POR) to explore all possible executions of a distributed Java application. Moreover, our approach provides a functionality to check the given distributed application against possible network failures which can occur at the operating system or the hardware layer.