The following program does not compile:

class A<X> {
    class B<Y> {}

    A<? extends Integer>.B<String> b;
    Object o = (A<Integer>.B<String>[][])b;
}

OUTPUT:
maurizio@maurizio-laptop:~/Desktop$ testws/dist/bin/javac Test3.java
Test3.java:5: ')' expected
Object o = (A<Integer>.B<String>[])b;
^
Test3.java:5: ';' expected
Object o = (A<Integer>.B<String>[])b;
^
Test3.java:5: illegal start of type
Object o = (A<Integer>.B<String>[])b;
^
3 errors