A. Sundararajan's Weblog

JavaOne 2006: Wednesday, May 17

Today I attended the following talks:

• Blu-Ray: Java Technology Goes Hollywood!
• Superpackages: Development Modules in Dolphin JSR-294
• Integrating XML into the Java programming language
• Java Memory Model: The building block of concurrency
• Understanding Mysteries of Java SE classloading

Blu-Ray: Java Technology Goes Hollywood!

I am a big fan of interactive TV -- atleast the kids can have something to do when watching TV rather than just sitting and watching passively I don't know much about interactive TV standards or Java standards in this space - although I know a bit of MPEG-4. Main points I learned from this talk:

• Blu-Ray uses different wavelength to record. Can record upto 8 layers. Atleast 25 GB of storage!! That is BIG storage!! Many things are possible...
• Blu-Ray supports a Java standard BD-J - which uses a profile on CDC configuration
• Compatible with cable TV Java standards -- which means you can write apps that can moved with minimal changes b/w cable-TV from/to blu-ray disc

Superpackages: Development Modules in Dolphin

As usual, Gilad Bracha presented nicely. JSR is in it's infancy. He explained the current strawman proposal of the development module. Someone asked why do you need two JSRs for module system for Java (development modules - JSR 294, deployment modules - JSR 277). Answer: Language design JSRs are different from other kind of JSRs. The focus of these JSRs are different.

Integrating XML into the Java programming language

This is XML literal support for Java. Mark Reinhold summarized why ad-hoc XML programming is hard in Java - he compared existing XML APIs such as DOM, JDOM, dom4j, XOM, StaX. Two proposals for XML literal syntax -- XML-like angular bracket or # to demarcate tags (he calls this Java-like). He did a "show of hands" poll for XML language support in Java. I voted for "no" -- I must admit that I am with the minority

Java Memory Model: The building block of concurrency

• No way two threads can communicate without synchronization.
• reordering of instructions, memory fetches, related compiler/proecessor optimizations can result in non-intutive results.
• Use synchronized blocks/methods -- don't be clever-- "there is only a thin line b/w being too clever and stupid"! (I liked this punch line)
• Double checking idiom works only if you make the double checked field as volatile (and you are using JDK 5.0 or above)
• Use java.util.concurrent classes whenever possible - don't reinvent the wheel and code similar data structures.
• Testing does not prove correctness with concurrency.

Understanding Mysteries of Java SE classloading

Nice summary of classloaders from JDK standpoint and HotSpot JVM standpoint. Only 2/3 people were interested in "loader constraints". Main take-aways:

• Avoid writing classloaders -- try to use java.net.URLClassLoader if possible
• If not, extend URLClassLoader and just override findClass and findResource methods only.
• Better to use single-parent-delegation model
• -XX:+TraceClassResolution can be used to debug class resolution/loading

( May 18 2006, 10:02:34 PM IST ) Permalink Comments [2] | | | | |