Real time Java
Java's sophisticated memory management, native support for threading and concurrency, type safety, and relative simplicity have created a demand for its use in many domains. Its capabilities have been enhanced to support real time computational needs:
- Java supports a strict priority based threading model.
- Because Java threads support priorities, Java locking mechanisms support priority inversion avoidance techniques, such as priority inheritance or the priority ceiling protocol.
To overcome typical real time difficulties, the Java Community introduced a specification for real-time Java, JSR001. A number of implementations of the resulting Real-Time Specification for Java (RTSJ) have emerged, including a reference implementation from Timesys, IBM's WebSphere Real Time, Sun Microsystems's Java SE Real-Time Systems, Aonix PERC or JamaicaVM from aicas.
The RTSJ addressed the critical issues by mandating a minimum specification for the threading model (and allowing other models to be plugged into the VM) and by providing for areas of memory that are not subject to garbage collection, along with threads that are not preemptable by the garbage collector. These areas are instead managed using region-based memory management.
Real-Time Specification for Java 
The Real-Time Specification for Java (RTSJ) is a set of interfaces and behavioral specifications that allow for real-time computer programming in the Java programming language. RTSJ 1.0 was developed as JSR 1 under the Java Community Process, which approved the new standard in November, 2001. As of 2006[update], RTSJ 1.1 is being developed under JSR 282.
See also 
- Real-Time Specification for Java (RTSJ)
- IBM WebSphere Real Time a fully conformant RTSJ SE VM
- JamaicaVM an RTSJ SE implementation with deterministic garbage collection
- PERC a real-time VM based on Java Standard Edition rather than RTSJ
- Sun Java SE Real-Time System
- Apogee real-time Java with real-time GC
- Timesys RTSJ implementation and testing toolkit
- jRate (Java Real-Time Extension) an open-source extension of the GNU GCJ compiler front-end and runtime system which adds support for most of the features required by the RTSJ.
- DDC-I Scorpion Java real-time Java SE, with safety-critical and secure versions.
- International Workshop on Java Technologies for Real-time and Embedded Systems (JTRES 2006) JTRES 2007 JTRES 2008
- LJRT Lund Java based Real-Time LJRT open source
- Fiji VM real-time Java
- Real-time Java VMs