This paper investigates the temporal behaviour of the Java run-time environment for real-time control system applications. A representative process controller is used as a case-study, and has been implemented in Java according to a number of proposed generic software architectures. These are assessed upon several general purpose run-time platforms, before extending the investigation to a claimed real-time Java environment. The investigation is then furthered, by compiling the Java into native code, in an attempt to improve execution time. The results prove surprising and indicate further directions in which to progress this technology.