The default install of Mac OS X 10.6 includes Java 6, or is it still Java 5?
On my Mac mini under OS X 10.6.5, a
java -version gives me Java 1.6.0_22.
It's an out of box + upgrade from 10.6.4 to 10.6.5 and installation of last Xcode 3.
Snow Leopard comes with Java 6, Leopard is J2SE 5. Just see any Java update support article for OS X 10.6 and there will be mention of Java SE 6 see here.
Snow Leopard comes with 64 bit Java 6.