I offered some publicly-disclosed users of real-time Java in answer to another question; I'll reproduce here:
The Real-Time Specification for Java
now has several commercial-grade
implementations:
Sun/Oracle's JavaRTS (now unavailable, it appears Oracle has disbanded the JavaRTS team and made the product unavailable, without communicating publicly about it)
- IBM's WebSphere
Real-Time
- Aonix PERC
- aicas JamaicaVM
- Apogee Aphelion
These products span the continuum from
compilation to native code (Aonix) to
J2ME (aicas, apogee), to full J2SE
(Sun, IBM). Most, if not all, have
seen deployments in small numbers of
safety- or mission-critical systems,
but momentum is building. Examples
include Eglin
AFB's space surveillance radar
modernization and the US Navy's
use of RTSJ in the DDG-1000/Zumwalt
destroyer. Sun also claims
deployment in the financial
transaction processing domain.
If you are interested in RTSJ, I
suggest Peter Dibble's Real-Time Platform Programming, or Professor
Wellings' Concurrent
and Real-Time Programming in Java.
On a related note, there is also work
underway to provide a Safety-Critical
profile for the Java programming
language, built as a subset of RTSJ.
Also, an expert group has formed to
explore a Distributed RTSJ DRTSJ,
but the work is stalled.
Not all of the above refers to Sun's JavaRTS or even RTSJ; several vendors have pursued their own proprietary path for real-time Java because they feel the RTSJ doesn't match their customers' needs.
Some additional users I'm aware of now include Army Future Combat Systems and several of the DARPA Urban Challenge contenders.