Introduction to Real-Time Java

By michaelzyy and michaelzyy
Original article: http://www.matrix.org.cn/resource/article/2006-11-28/JAVA+Real+Time_72f1a994-7e38-11db-babc-9753a314dd4b.html

What does real-time mean?

Greg bollella, an outstanding engineer at Sun and one of the authors of Real-Time Java specifications, said, real-time means "the ability to reliably predict and control the time behavior of program logic." Real-time does not mean speed, as many developers think. It means that when we need to respond to real-world events, its behavior is predictable and reliable. Real-time Computers always respond within a limited period of time. Depending on the set period, a large number of systems can be called real-time.

Many programs cannot allow even a one-second delay; they include financial software, aircraft control software, nuclear power plant control software, and so on. Therefore, these are not all very high speed requirements, although real-time platform designers will try to make the program faster. Obviously, the standard Java platform does not meet the requirements of these real-time systems, which is also written into the j2se and J2EE license protocols, these protocols clearly declare that Java cannot be used in nuclear power plant facility software and defense systems.

Real-Time Java

Developing real-time applications requires a set of PI and semantics that allows developers to correctly control program running time and program behavior in reality. Therefore, the real-time Java version must provide some JVM enhancements and a set of Apis suitable for real-time programs. It is not surprising that the biggest obstacle to adding real-time features to Java lies in its garbage collector. Sun's recently released Java real-time version rts1.0 contains a revolutionary core real-time Garbage Collector. Although its first implementation does not contain such a garbage collector (will be added in the next release version ). Java RTS raises other issues to ensure Thread Scheduling certainty, overhead synchronization, lock queue management, class initialization, and minimal interrupt response latency. Java RTS only applies to suitable operating systems, which means that only real-time operating systems such as QNX are suitable for implementing such a JVM. *
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