As of Aug 4, 2009, the current version of Sun's Java client is Java(TM) 6 Update 15.
If you see the Java Update icon or "Java Update Available" balloon in the lower right corner of the screen, the latest version of Java should be ready to install. You can click the icon and follow its prompts to apply the update. Note: We recommend that you do not install any offered "extras" like the MSN Toolbar, OpenOffice.org Installer or Microsoft's Bing. Please un-check these options if they appear.
Or, our How To Update Sun's Java Software, http://it.cas.psu.edu/260.htm, has complete steps on how to install Java from either the "Java Update Available" message or how to download and install Java manually .
This release contains fixes for one or more security vulnerabilities. The full list of changes may be found here: http://java.sun.com/javase/6/webnotes/6u15.html
Previously, older versions of Sun Java were not removed from your computer when you updated. You had to manually remove older versions of Sun Java from your computer. This has now changed. You no longer need to remember to remove the previous Java version.