William Martinez

Thanks Ed.
Actually sounds like a good support. And thanks for the source code link!


William Martinez Pomares.
Architect's Thoughts

Hello.
Not quite sure if you cover this in the chapter named The Connected World, but some the times the phone may be a front-end device where a client app consumes back-office services. That means we will need at least HTTP to do some requests. Is there any web services (read SOAP) or REST helper libraries?
How is the usual service consumption treated in mobile, and particular Android.

Now, as opposed to iPhone, Android does allow for concurrency (I mean, several tasks running in my app). Is there a model for a back - thread that frequently consumes a service to simulate a "push" of information into the phone? Imaging people that want to continuously post their position into a mapping system. Ideas for that?

Thanks.

William Martinez.

Hello.
As a member of a development company, we are actually in constant improvement of our interviewing techniques. I've found that specific knowledge on the tool or language may not mean the developer is actually good on solving abstract problems or, even more today that is needed, integration with other technologies, languages or platforms.

I know the book is not a total bible for the interviewer, but a companion when the position is related to Java/J2EE. Is there a guide on how to use the book, I mean, tips a tricks that will guide the interviewer to follow the answers (validation tables, redirection of the questions, validation of the actual answers, etc). I can find several sites with lots of questions about Java and other technologies on the internet, but had not find yet a good interviewers guide that will go the next step. HOw do you see this book in that context?

Thanks!

William

Thanks a lot for both answers.
We will try out your suggestions. Of course I cannot tell if they worked until the next OOM, which we cannot predict when will it occur.
Thanks!

William.

Hello.

We are facing an OOM in production, that shows intermittently, with any load and in any function of the application.

I know that sounds not new to all. Anyway, We need advice on how to solve the problem. So, here is a list of questions.

1. Using a HeapDump and several analysis tools, we were not able to find any memory leak. We have enough memory and a -Xms512m -Xmx784m setting. Nevertheless, the dump file is just 115mb or less. Can we compare that? Is that size a clue we can use to determine the problem is somewhere else and not actually that the memory is being totally consumed?

2. Now, if the above holds true, and there is actually memory unused (wonder how can we totally be sure of that), how come the JVM throws the exception?

3. I read something about the different memory "sections" to hold object of different ages (GC generational model). Is if possible some of those sections are not growing although there is memory to use? How can we fine tune those settings, if there are settings for that?

4. Further more, we are working in this config:
Jboss 4.0.1sp1
JVM 1.4.2_12
Operating System W2K3 SP2
Could it be and older JMV-New O.S conflict problem?

The actual error is:
Unexpected Error; nested exception is:
java.lang.OutOfMemoryError
java.rmi.ServerError: Unexpected Error; nested exception is:
java.lang.OutOfMemoryError

5. Unexpected Errors. Should this mean an error captured at JVM? That is, the exception is not caught during normal execution like creating an object or going through a loop. Our guess it is thrown when actually executing the GC. How can we sure of that? If that is correct, does it mean is it a JVM problem?

Thanks for your help.
William.