For the first time, Sun is updating Java this year providing fixes for over 300 bugs. While the total bug tally may seem high, the latest Java update more about enhancing features and performance than it is about security fixes.

That’s because Java SE 6 Update 18 (also known as 6u18) does not include any security updates at all—unlike its predecessor, Java SE 6 Update 17, which was released in November 2009 and included fixes for multiple vulnerabilities. Still, that doesn’t make the new update—which may turn out to be the last from Sun (NASDAQ: JAVA) before it is acquired by Oracle—any less significant.

To Dave Hofert, senior group marketing manager for the Java Platform Group at Sun, the release marks a high-water mark for Java.

According to Hofert, the largest improvement in this release is the performance work that we did for our virtual machine, called HotSpot. “This helps improve performance for both Java and JavaFX applications.” After that, we have improved the usability of the Java installer (we have replaced the underlying installer mechanism) and of Java Web Start applications,” with a clearer progress bar, he said.

Other improvements in 6u18 usher in still more performance gains. For instance, with the new release, Sun noted that that jar file creation is faster.

The 6u18 release notes state that the fix of a long-standing bug related to jar file creation has greatly improved creation time. It also improves the startup time for Java applications and applets. JavaFX, in particular, gets a runtime speed boost. JavaFX is Sun’s effort to create an RIA that aims to compete against AJAX, Flash and Silverlight. With the 6u18 update, Sun’s efforts have improved the start of JavaFX applications by as much as 15 percent, it said.

The performance of user interface (UI) applications also gets a boost by way of smaller memory consumption by text rasterizer and faster processing of images. Memory handling overall has been improved with the 6u18 release as well.

The Sun release notes state that in the Client JVM (Java Virtual Machine), the default Java heap configuration has been modified to improve the performance of today’s rich client applications. “Initial and maximum heap sizes are larger and settings related to generational garbage collection are better tuned.”

With Java SE 6 Update 18, Sun has also makes it possible to read larger .ZIP files of up to 4 gigabytes in size. Previous Java releases were limited to being able to read .ZIP files of only 2GB or less.

Java Security Updates to Come

Sun provides two different types of Java updates: General releases with bug fixes and enhancements, such as 6u18; and security-only updates, which take place three times a year.

“The reason we do this is that many enterprise customers wish to adopt the security updates as fast as possible and we try to minimize the number of changes so as to minimize our customer’s testing cycle,” Hofert said. He added the next security release will occur later this quarter.