When compiling this code:

public class OuterPlusEnum {
        enum E {
                E1
        }

        public int m (E e) {
                switch (e) {
                        case E1:
                                return 0;
                }
                return -1;
        }
}

The CP for classes OuterPlusEnum$1 and OuterPlusEnum will have an empty UTF8 corresponding to the empy name for class OuterPlusEnum$1. This entry could be saved with a simple check on the class name.