Real-time Specification for Java

Real-time Specification for Java (RTSJ) (Wikipedia), one of the Java Technologies, enables Java developers to write Java Standard Edition programs that run with, as IBM puts it, "predictable response times." As Sun puts it, an RTSJ implementation "enables the creation, verification, analysis, execution, and management of code written for the Java platform for which the correctness conditions, timeliness, and execution predictability are paramount."

RTSJ was the very first JCP [JSR]: JSR 1. See Real-Time Java (It's About Time).

IBM has an RTSJ impl, WebSphere Real Time.