Apple just released a developer preview of the long overdue Java 6.
It’s Leopard only (10.5.1 actually), requires 64-bit (Core 2 Duo or Xeon), and again is a “developer preview” only. To get it, go to the developer site, https://developer.apple.com/ and log in (or sign up (free) and log in) and go to the downloads section.
Leopard 10.5.2 is expected to be released in January at Mac World and should include Java 6.
Some more details here:
https://www.tuaw.com/2007/12/19/java-6-developer-preview-now-available-for-leopard/