if I understand correctly according to following assertion from JLS 15.9.5 anonymous classes are always final:

    An anonymous class is always implicitly final (§8.1.1.2).

But reflection API reports that the class is not final. Namely let's consider following code:

    import java.lang.reflect.Modifier;

    public class Test12 {
        static class Foo<T> {}

        public static void main(String argv[]) {
            Foo<Integer> foo = new Foo<>() {};
            if ( (foo.getClass().getModifiers() & Modifier.FINAL) != 0 ) {
                System.out.println("final, modifiers: " + foo.getClass().getModifiers());
            } else {
                System.out.println("not final, modifiers: " + foo.getClass().getModifiers());
            }
        }
    }

On JDK9b69 it reports:

    not final, modifiers: 0

javap reports:
final class Test12$1 extends Test12$Foo<java.lang.Integer>
  minor version: 0
  major version: 52
  flags: ACC_FINAL, ACC_SUPER

This seems to be a discrepancy between spec and javac (VM? reflection API?) which should be fixed.