Java generics SuppressWarnings(“unchecked”) mystery

Question

Why does code alternative(1) compile without warnings, and code alternative(2) produce an \"unchecked cast\" warning?

Common for both:

class Foo         


        

Answer 1

It's a bug in both Oracle and OpenJDK 7 and 8.

You can't (shouldn't) get compile warnings/errors from reordering declarations in a class.

Runtime errors, yes; compiler errors, no.

This is Bug 8016636 (thanks for filing it), but there's been no activity in over a year.

Unfortunately, that is not uncommon in Oracle's bug tracker.

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Additional weirdness:

• The warning is suppressed if EMPTY_ARRAY is not final.

• Ironically, the warning is suppressed with if you initialize it with a non-array, e.g. Object EMPTY_ARRAY = new Object(). (But don't do that...)