Apple has made available Java 2 Platform Standard Edition (J2SE) 5.0 Release 3 through the Software Update utility.
Here is the description provided by Apple:
Java 2 Platform Standard Edition (J2SE) 5.0 Release 3 includes version 1.5.0_05 and improves functionality of J2SE 5.0 on Mac OS X v 10.4 Tiger 10.4.2 and later. This release does not replace the existing installation of J2SE 1.4.2.
For more details on this Update, please visit this website: http://docs.info.apple.com/article.html?artnum=302412