1Z0-809 Question #2: Real Exam Question with Answer & Explanation

Given the class definitions:

class Alpha {
 public String doStuff(String msg) {
 return msg;
 }
}

class Beta extends Alpha {
 public String doStuff(String msg) {
 return msg.replace('a', 'e');
 }
}

class Gamma extends Beta {
 public String doStuff(String msg) {
 return msg.substring(2);
 }
}

And the code fragment of the main() method,

12. List<Alpha> strs = new ArrayList<Alpha>();
13. strs.add(new Alpha());
14. strs.add(new Beta());
15. strs.add(new Gamma());
16. for (Alpha t : strs) {
17. System.out.println(t.doStuff("Java"));
18. }

What is the result?