Java noob: generics over objects only?

Question

I\'m new to Java. While coding a Map<>, I found out that declaring Map is a syntax error while Map is OK

Answer 1

Is it only possible in Java to instantiate generics over object types, as opposed to primitives?

correct.

If so, is there a noticeable performance penalty for boxing/unboxing of primitives?

yes, there is.

See here for a detailed description: http://java.sun.com/j2se/1.5.0/docs/guide/language/autoboxing.html