Only Java updates for Mac is through the Software Update, and other than older OS X system not having recent updates for Java they did have it (unless maybe it's an early version of OS X).
I don't know if there was a standalone app for it at all on the older versions of OS X, but otherwise if it is using OS 9 then you would have to find it online somewhere as if I remember correctly that OS did have a standalone installer available from Sun. However, OS 9 did have a software update as well in the control panels which does still work though I don't know if Apple "controlled" their version of Java back then.