[oblio]

My guess? Lack of first class functions and macros. Maybe higher kinded types.

The first one is annoying, not really something a professional software developer would care about for more than 10 minutes while creating a new product.

Macros can be major footguns, they're something that can only be realistically used efficiently and safely in large code bases by actual senior engineers. So the jury's still out how much they really increase productivity for the averaged developer.

Higher kinded types seem great, but it seems that they're not easy to implement and they also slow compilation down a bunch (someone please correct me on this). These seems hard to bolt on to an existing language, so Java can't be faulted much.

[smitty1e]

Java itself may lack macros, but by the time you get in reflection and libraries with XML and compile-time magic to work around the lack of macros and the whole thing is a giant plate of spaghetti, maybe macros were no' so bad after all.

[rendaw]

Those would've been my guesses too, but Java's had first class functions in the form of anonymous classes since 1.1, and as the other commenter mentioned reflection takes care of a lot of macro use cases.