Weiqi Gao's Observations

Friday Java Quiz: What's Your Favorite Java 7 Feature...

Like in past years, I'm following JavaOne from afar. All I have access to are the general sessions and attendee's blog reactions to specific sessions on JavaLobby, java.net, JavaBlogs, and StuffThatHappens. And on Tuesday's session, I heard Danny Coward talking about new features for Java 7,

which, BTW, is scheduled for Summer of 2009.

This, I suppose, is the same talk as the one I mentioned 509 days ago. However, the scope has clearly shrunk quite a bit.

Today's quiz is a rhetorical one:

Q: What is your favorite new Java language feature that did not make it into Java 7?

I'll start with mine:

XML literal (I'm virtually alone on this one, but still...)
Properties (can anyone tell if it's in or not?)
Reified types for Java generics (Erase Erasure, as I've call it 475 days ago)

Scott Bale: What's So Great About Guice

Scott Bale's presentation about Guice at the St. Louis JUG tonight is well attended and lively.

You can tell Scott liked Guice. He enumerated all the things about Guice that he liked at the beginning of the talk: small, simple powerful, type safe, no xml, easy to use, etc. It's been my experience that people either really like Guice, or they don't care for it at all.

Scott did the brave thing—he did the presentation mostly in Eclipse, with only a few slides. So once again this is one of those "you have to be there to appreciate it" deals.

The presentation is based around a set of simple examples that covers the basic features of Guice. Content-wise, this presentation is similar to what you can find in Google Video. The interesting bits are the conversations with the audience members. Jeff Grigg, Kyle Cordes, Michael Easter, Rob Smith, Dean Farwell, Jeff Cunningham, et. al. were on hand to make the evening a thought provoking and entertaining one.

As for me, I was too tired from moving my daughter back home from school this afternoon and couldn't focus too well on the code on the screen. And I caught the mentioning of Modules, Injectors, Annotations, Scopes, Providers, SINGLETONs, and the binding DSL. Oh, and we did not bash Spring Framework. Honest.

But no worries, the slides and code samples will be posted on the website in a moment.

JavaFX FAQ 1: Why The UnsupportedClassVersionError

I was asked a JavaFX Script question yesterday that I think other people may encounter, especially the Mac OS X folks who are trapped in a non-"64-bit-Intel-Leopard" (Core Duo, P5, P4, etc.) machine (who are therefore still without a Java 6 JDK).

Q: I downloaded the JavaFX Script compiler from http://openjfx.java.sun.com/ (which seems to be down at the moment).
So I have a openjfx-compiler directory with dist/bin/javafxc and dist/bin/javafx inside it.
I'm trying code sample 1 from http://java.sun.com/developer/technicalArticles/scripting/javafx/ria_1/.
It compiles with javafxc, but when I run it with javafx I get the following.

Note that I'm using Java 1.5.
Any idea why this doesn't work?

I seem to remember the same problem being asked on the mailing list a while back. So I went to the mailing list archive to find the answer. Since it took me quite a bit time to find the answer, I thought I'd post the link here.

Tom Ball (on openjfx-compiler mailing list):

You need to compile with "-target 1.5" on the Mac, at least until Apple 
ships Java 6.  The compiler generates Java 6 versioned class files by 
default, since we are extending the latest version of javac.

Tom

Patrick Wright wrote:
> Hi
> 
> I have sync'd with the trunk, built the compiler, and was able to
> compile Jim Weaver's simple test program at
> http://learnjavafx.typepad.com/weblog/2007/11/developing-your.html.
> Trying to run it I get the following:
> 
>> javafx CompiledHelloJavaFX
> Exception in thread "main" java.lang.UnsupportedClassVersionError: Bad
> version number in .class file
>         at java.lang.ClassLoader.defineClass1(Native Method)
>         at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
...