多选题 Given:
2. class Ball {
3. static String s = "";
4. void doStuff() {s += "bounce "; }
5. }
6. class Basketball extends Ball {
7. void doStuff() {s += "swish "; }
8. }
9. public class Golfball extends Ball {
10. public static void main(String[] args) {
11. Ball b = new Golfball();
12. Basketball bb = (Basketball)b;
13. b.doStuff();
14. bb.doStuff();
15. System.out.println(s);
16. }
17. void doStuff() {s += "fore "; }
18. }
What is the result?