Well, you can learn the syntax but the problem is when someone says they "know java" usually you care about them not just knowing java syntax, but the pitfalls, many frameworks that exist, general approach to problems, etc.

Just because I know Java + Ruby Syntax + Some stuff on RoR does not mean I am a good RoR programmer, there's just so much more to RoR than the syntax.

I want to see someone completely grok pointer logic in 24 hrs from knowing nothing.