Contest question: Java code about method overwriting

Question:

I took a quiz and got the following question:

Check the alternative corresponding to the result of executing the main method of the Java program presented below:

 public class A { public void ml(){ mx(); } public static void main(String[] args){ A a = ( B) new C(); a.m1(); B b = (B) new A(); b.m1(); } public void mdx(){ System.out.print(10); } } class B extends A{ public void mx(){ System.out.print(30); } } class C extends B { public void mx(){ System.out.print(40); } }

a) The value 40 and the value 10 will be printed
b) The value 40 and the value 30 will be printed
c) The value 10 and the value 10 will be printed
d) The value 40 will be printed and the ClassCastException exception will be thrown later
e) The value 10 will be printed and the ClassCastException exception will be thrown later

Note: I saw that there is a blank space in: ( B)

The template says that the correct one is the letter D, but I have doubts about this question. Is this template correct? If yes, why? And if not, too, why?

Answer:

There are compilation errors in this code:

• Within the ml() method of A , the invoked mx() method does not exist in class A . I think the mdx method was supposed to be called mx .

• In main a method called m1 is being invoked, not ml . I think these names were supposed to be the same.

See this not working in ideone:

Main.java:4: error: cannot find symbol
    mx();
    ^
  symbol:   method mx()
  location: class A
Main.java:10: error: cannot find symbol
    a.m1();
     ^
  symbol:   method m1()
  location: variable a of type A
Main.java:12: error: cannot find symbol
    b.m1();
     ^
  symbol:   method m1()
  location: variable b of type B
3 errors

_{^{Note: This Main.java is because I'm compiling on ideone (and I had to take the public out of the declaration of A ), this is just a limitation of ideone. If you are going to compile it yourself, it will show A.java instead of Main.java .}}