Sun Microsystems has confirmed that a last minute hitch has delayed Thursday's expected launch of an update to Java.

The upgrade, with the cumbersome name (Java Platform Standard Edition 6 Update 10, or Java SE 6 u10), is not just an incremental release, but rather it features technology that is considered critical to reviving the concept of client-side Java applets.

Applet startup times are improved and applets can be turned into desktop widgets via different improvements in Java SE 6u10. Java SE runs on both desktops and servers.

The upgrade had been slated to appear today (Thursday), but a Sun representative said on Wednesday that the release would be delayed until an as-yet undetermined time. A last-minute issue apparently emerged during final testing.

Among the highlights of the update is Java Quick Starter, providing an enhanced runtime experience by significantly improving Java application and applet startup times, Sun said.

"We've structured the way the Java runtime starts up so the elements associated with starting an applet, or starting an application, produce results that are visible on the screen quicker," said David Bryant, senior director for Java marketing at Sun.

Sun says that Java SE 6u10 also offers a new method of getting Java software to run faster, via Java Kernel. With this feature, users download a kernel featuring the most commonly needed Java Runtime Environment (JRE) components. When additional components are needed, they are downloaded as needed. Users no longer need the full 14.5MB kernel.

"Now, you just install a 4.5MB initial piece of the Java kernel and that's enough to run common applications and applets," Bryant said.

Although Java initially was hailed in the mid-1990s as a way to run client-side applets, the platform instead became known for its server-side capabilities. But applets are useful in delivering web application functionality such as charting and data analysis, Bryant said.

"Applets have swung back to being a popular way of delivering functionality through the web," Bryant said.

The Java update has been viewed as a companion to Sun's new JavaFX technology for rich Internet applications.

"The release of Java SE 6u10 is important because it solves the JRE and Java application deployment issues," in which the entire runtime had been required, said Java developer Jim Weaver, of JMentor and author of a JavaFX blog. "These issues have kept rich-client Java from being feasible for most applications - until now. I'm looking forward to a future that includes wide use of rich-client Java and JavaFX and I'd like to see Apple follow suit [and support the Java update on MacOS] so that Mac users can enjoy the same deployment benefits and JRE ubiquity."

Weaver noted that Google's new Chrome browser requires Java SE 6 u10 to run Java applets.

Another boost for applets is inclusion of a built-in Deployment Toolkit in Java SE 6u10. This ensures that users are running the most recent version of Java SE. This makes it easier to deploy applets or Java Web Start programs, Sun said.

Also highlighted is the capability to drag applets directly from a browser and run them as desktop widgets. This is being done by a new implementation of the Java Plug-in. "Browsers don't need to embed the Java [virtual machine] in them. Bryant said.

The release candidate for Java SE 6 u10 is available online.