Toward libraries for real-time Java

Reusable libraries are problematic for real-time software in Java. Using Java's standard class library, for example, demands meticulous coding and testing to avoid response time spikes and garbage collection. We propose two design requirements for reusable libraries in real-time systems: worst-case execution time (WCET) bounds and worst- case memory consumption bounds. Furthermore, WCET cannot be known if blocking method calls are used. We have applied these requirements to the design of three Java-based prototypes: a set of collection classes, a networking stack, and trigonometric functions. Our prototypes show that reusable libraries can meet these requirements and thus be viable for real-time systems.