Update 10, 29 June 2011 - This release updates J2SE 5.0 to 1.5.0_30, and updates Java SE 6 to 1.6.0_26. J2SE 1.4.2 is no longer being updated to fix bugs or security issues and remains disabled by default in this update. Support for out-of-process Java applets on Mac OS X 10.5 Leopard has been removed with this update.
This release is only for Mac OS X 10.5.8 or later versions of Mac OS X 10.5. http://support.apple.com/kb/DL1359
and for Snow Leopard:
Note: Java 1.6 for Leopard is 64 bit only, but for Snow Leopard it is available for both 32 and 64 bit.
But since August 2012 updates for Java (and especially Java Runtime Environment, which is what you actually need) must now be downloaded direct from Oracle:
Further information here: