Home > Articles > Programming > Java

David Holmes on Java Real-Time Systems

  • Print
  • + Share This
Dr. David Holmes, Senior Java Technologist and co-author of The Java™ Programming Language, 4th Edition, and Java Concurrency in Practice, talks with Steve Haines about Java Real-Time systems, concurrency, and JavaOne.
Like this article? We recommend

Dr. David Holmes is a Senior Java Technologist and currently a member of the engineering team developing Sun Java Real-Time System at Sun Microsystems. He's also co-author of two books, The Java™ Programming Language, 4th Edition, and Java Concurrency in Practice. Steve Haines, host of the InformIT Java Reference Guide, caught up with David right before this year's JavaOne conference.

InformIT: You have a robust background, both professionally as well as in publication, in Java Real-Time Systems, can you tell us how you got started in it?

David Holmes: My interest in real-time goes back to my undergraduate days in computer systems engineering when I did my thesis on the design and implementation of a real-time microkernel on a microcontroller. My PhD work took me more generally into concurrent systems and synchronization in object-oriented systems, which is when I got heavily involved with Java. I saw a lot of the early discussion papers on real-time Java, and at one stage almost became part of one of the groups investigating it in detail. But then JSR-01 (the Real-time Specification for Java) was formed and I concentrated on my PhD, just keeping an eye on things as drafts of the specification were released, and annoying people like Greg Bollella and Ben Brosgol (both on the JSR-01 expert group) with a lot of questions.

About 18 months after my thesis was complete, some associates in the US had the opportunity to work on a DARPA funded research project in which they were going to implement the RTSJ, and they asked me to join them. Naturally I said yes. That led to a lot of interaction with the JSR-01 Technical Interpretation Committee (which was a fancy name given to the small group of people who volunteered to look after JSR-01 maintenance and updates), and that in turn led me being invited to join the TIC, and later the expert group for JSR-282 (RTSJ 1.1).

That project wound up in 2004. By late 2005 Greg Bollella wanted me to join his team at Sun Microsystems. I joined Sun at that time, working on the Hotspot VM, and eventually made my way into the engineering team for Sun's Java Real-Time System, which is where I am today.

IT: The Java Community Process started many years ago with JSR-01, for which you are a member of the Technical Interpretation Committee. What have you see change in Real-Time Java Systems since the inception of JSR-01? How far have Java Real-Time applications come in that time?

DH: Surprisingly, I haven't seen a huge amount of change since JSR-01 was first released in 2000. Primarily, I think, because the RTSJ was "ten years ahead of its time" as Tim Lindholm (former Distinguished Engineer at Sun) said to me back in 2002. It took quite a while for people to seriously consider using Java for real-time, and in particular using the RTSJ, in part because it took quite a while for commercial quality implementations to emerge.

What has happened though, is that there has been pressure on traditional VMs to become more predictable. For a long time it has all been about throughput, throughput and throughput, but as large scale applications put more and more strain on the VM, these applications have started to suffer from the non-determinism in such systems, and in particular the unpredictable latencies of garbage collection. This has led to the development of so-called low-pause collectors for traditional VMs. In addition interest in the use of the RTSJ for application domains that are definitely not what you would consider traditional real-time domains, has grown considerably. This is particularly so in financial systems — and there are a couple of sessions at this year's JavaOne discussing these areas.

IT: I see that you're a member of JSR-166, the Expert Group defining concurrency utilities. Can you tell us a little bit about JSR-166 and what types of specifications it is turning out?

DH: JSR-166 defines the contents of the java.util.concurrent package, which is a toolkit for concurrent programmers — which, as Java is inherently concurrent, is pretty much all Java programmers. It was first introduced in Java 5 and has had some further enhancements in Java 6, and planned ones for Java 7. It's really about making effective concurrent programming achievable by the average Java programmer — though it caters for beginners through to advanced experts.

IT: Many people still believe that Java, and any interpreted or partially interpreted language, is not suitable for developing real-time systems. Is there anything you can tell us to dispel that misconception?

DH: Being able to develop real-time systems is all about managing non-determinism so that an application's behaviour is predictable. This has to apply through all layers — from the hardware to the application code. Because people tend to think of the Java platform in its entirety, they think the complexity prohibits achieving predictable behaviour. But by managing different aspects of the platform — in particular memory management, and thread scheduling — you can get that predictability: which is exactly what the RTSJ set out to define. This doesn't mean that any arbitrary piece of Java code can magically become predictable — you have to adapt the programming model and how you use the platform features: for example, by ensuring that classes are loaded and initialized before the time-critical portion of your code, and perhaps by ensuring that code has also been compiled. In addition, outside of the RTSJ, real-time garbage collectors have become reality, allowing the use of Java in a broader range of applications, extending through soft-real-time to more traditional hard real-time. There are even efforts under way (JSR-302) to extend Java into the safety-critical domain.

IT: What are some examples of real-time systems written with Java?

DH: Well, some of the ones I can tell you about have been showcased at past JavaOnes. For example, last year Sun previewed its "BlueWonder" system, which is an industrial strength PC running Solaris 10 and Java Real-Time System, for use in industrial automation and control (and on show again this year). There was also the Tommy autonomous vehicle that used real-time Java. In the earlier DARPA project I mentioned, we had, we believe, the first example of real-time Java flying — that was executing mission control software on an un-manned aerial vehicle (UAV). In addition there have been past public announcements, such as the ITT Eglin Space Surveillance Radar's "Control and Signal Processing Upgrade" program.

IT: I see that you're presenting a Hands-On Lab entitled "The Real-Time Java Platform Programming Challenge: Taming Timing Troubles." Can you give us a sneak preview of what to expect from this presentation?

DH: Hands-on Labs are all about getting your hands dirty. What we do with the Java Real-Time lab is introduce people to some of the basic APIs and features of the RTSJ and get them to flesh out some code skeletons to get a simple real-time application running. But then we show how the code, while functionally correct, can sometimes miss deadlines and fail to be real-time. We then employ a new tool we have, the Thread Scheduling Visualizer, to examine what happens during the execution of the application and to discover why deadlines are missed. That information can then be used to correct the code, taking into account things that in a non-real-time environment the programmer doesn't have to think about: priorities, scheduling and priority inversion. In this way people get a taste of the RTSJ and the tools we have with Java RTS, and learn that real-time involves thinking about more than just the basic functional code.

IT: What are you particularly excited to see at this year's JavaOne?

DH: Well I'm very pleased that real-time finally has its own track! Though we let a couple of the other technologies (Embedded and JavaCard) share it with us. :) This shows how interest in real-time is expanding.

IT: What's next for you? What are you working on?

DH: Working on a product engineering team, what's next for me is whatever is in the next version of our product. As we're releasing Java RTS 2.2 in the very near future (beta available now), what's after that is something you'll just have to stay tuned for. :)

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020