Editor's Daily Blog

Playing the Game

Picking up discarded objects and putting them back in the toy box

So, here's an amusing analogy for you, from Danny Coward, Sun's Chief Architect for Client Software:

Like using the living room as the kids play area, tidying up, or garbage collection, is an integral part of life in the JVM. Except that the kids are applications and the toys on the floor the objects they create. But unlike in your living room, these kids don't sleep, are always playing with something, will scream if they have to wait while you tidy up, and will get seriously, seriously mad if they lose a toy. So how can you organize the mess they make without disrupting the game ?

Well, I suppose one answer would be to use Real-Time Java, but all that does is to make the timing of the cleanups predictable, potentially at the expense of performance (i.e., how many toys you get to play with in a given timeframe). But we can do better than that, right? Danny continues:

The HotSpot team has been quietly working on a new algorithm, called Garbage First, for tidying up the memory space in the JVM while the kids are playing, as a replacement for the existing parallel and concurrnet mark sweep collectors. By dividing the living rooms into equal squares, it turns out that for most games, many of the squares contain unused toys that can be safely put away.

This approach could have some interesting consequences. Being scheduled, it's highly predictable, and by dividing the work up, it's highly parallel, and thus well-suited to multi-core. Sound good? Well, you can try it. As Danny reveals in Java VM: Trying a new Garbage Collector for JDK 7, this garbage collector has already been added to the latest build of JDK 7.

Also in Java Today, Eduardo Pelegri-Llopart announces that Sun has launched a Tomcat and GlassFish Survey. "We are conducting a survey on developers, ISV, etc, that are using Tomcat and are considering GlassFish. We want to find out what features are used and which migration approach would be preferred. If you want to help us, please participate in the survey. Thanks!"

"With the recent announcement of GlassFish v3 "Prelude", Sun's OSGi-based Java EE 6 server, the use of OSGi across the enterprise has grown to encompass almost all of the back-end servers." In the InfoQ article OSGi in the Enterprise, Alex Blewitt looks at how OSGi usage is growing in open-source projects, webapp and back-end systems, and OSGi's longer-term prospects in the enterprise.

New Java plug-in concerns top today's Forums, with leathrum reporting of an Applet not compatible with new plugin. "I have an applet which works fine with the plugin version 1.6.0_10 in classic mode, but not in next-generation mode. The page is written in XHTML, using <object> tags following the W3C standard, and uses LiveConnect to communicate with JavaScript. The JavaScript fails at the first call to a method defined in the applet. Also, even though I have the Java console configured to appear whenever an applet runs, it does not appear for this page, so I have no evidence that the applet is actually initializing. I know the security model for LiveConnect has changed, but it is also supposed to be backwards compatible. Is there something I need to change in the <object> tag attributes or in the JavaScript to get this applet working in the next-generation plugin mode?"

Meanwhile, kbr sets the record straight on the modern applet life-cycle in the follow-up Re: Dragable applets -- you screwed that up too... "The current applet lifecycle behavior is as intended. When applets were first introduced in HotJava, multiple calls to start/stop were allowed, and the applet instance would be cached between visits to the same web page. This behavior was changed several releases ago to no longer cache applet instances by default. This means that you will get calls to init / start upon visiting a page with an applet, and stop / destroy upon leaving the page. It is possible to request the previous lifecycle behavior, but I strongly recommend against it, even though the implementation of this functionality works well in the new Java Plug-In. Google for "legacy lifecycle" There are no explicit events in the current browser plugin specifications for minimizing the browser window or switching to a different tab. This makes implementing calling stop() / start() upon these events basically impossible."

ankitmittal000 has some questions about the potential benefits of Inplace execution in CLDCHi. "I am working on Inplace execution feature given by SUN in CLDC Hot spot Implementaion. I want to know how much performance can be increased by using inplace execution for the midlet to be run on the device. I have converted the midlet jar file into application image (bun) but not able to know whether I have got any significant improvement or not. Can anybody tell me that how can inplace execution improve the performance and it will affect which part? Is there any way to know how much performance has been increased like some benchmark midlet for InPlace Execution feature."

Finally, Bill Foote updates the state of Blu-Ray Disc Java specs and realities in Re: [BD-J-DEV] Issue with remote colored buttons. "I should mention that sample code 19.2 might be a bit overkill, since subsequent to the book's publication, the BDA added a requirement that the HAVi API return exact color values. The whole fuzzy match on hue isn't necessary for players that obey the enhanced spec. That said, I'd want to do extensive player testing before counting on that spec requirement having been implemented everywhere that matters; all things considered, it's probably worth it to be conservative, and add the tiny bit of code for the fuzzy match."

Today's Weblogs begin with Gabriele Carcassi writing about Scripting Java with Javascript: trapping Swing events. "As part of my current project, I developed a call that allows me to attach javascript to Swing events. This allows a third party to get my packaged applets, and integrate them with their systems my running their own code in the same page."

Varun Nischal reports on his integration of Ant, Hudson and Glassfish. "Blogging after a long time, I have learn something interesting and would like to share with you all. Its all about automating builds and continuous integration!"

Finally, Jean-Francois Arcand discusses Who support what with Comet or why GlassFish v3 Prelude is for you! "Today JavaLobby is publishing an article about who does what in Comet, and how. Time to try GlassFish v3 Prelude to taste Comet!"

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