The latest release of Sun's Java has finally been deemed good enough for OS X users. By default the JVM in OS X is J2SE 1.4.2. Wondering if an updated iTunes (to address some recent security issues) would be released, I clicked Apple > Software Update... tonight. No iTunes in sight, but a welcomed Java update was discovered. However, J2SE 5.0 R3 will apparently coexist with J2SE 1.4.2 as mentioned in the installer:
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.