[SCJP] Generics questions form SCJP 5 study Guide

[Haithem Jarraya]

Hi,
I am reading the SCJP Study Guide by "Kathyy Sierra" and "Bert Bates", in the Generics chapter there is this question that I tried to comiple it but I am having compiler error.
here is the questions:

 Given a method declared as:
public static <E extends Number> List<? super E> process(List<E> nums)
A programmer wants to use this method like this:
// INSERT DECLARATIONS HERE
output = process(input);
Which pairs of declarations could be placed at // INSERT DECLARATIONS HERE to allow
the code to compile? (Choose all that apply.)
A. ArrayList<Integer> input = null;
ArrayList<Integer> output = null;
B. ArrayList<Integer> input = null;
List<Integer> output = null;
C. ArrayList<Integer> input = null;
List<Number> output = null;
D. List<Number> input = null;
ArrayList<Integer> output = null;
E. List<Number> input = null;
List<Number> output = null;
F. List<Integer> input = null;
List<Integer> output = null;
G. None of the above.   

answers

   Answer:
� 3 B, E, and F are correct.
�˚ The return type of process is definitely declared as a List, not an ArrayList, so A and D
are wrong. C is wrong because the return type evaluates to List<Integer>, and that can't
be assigned to a variable of type List<Number>. Of course all these would probably cause a
NullPointerException since the variables are still null�but the question only asked us
to get the code to compile. 

ok now here what I put In my code to check if its working or not

  public static void main(String [] args){
ArrayList<Integer> input = null;
List<Integer> output = null;
output = process(input);
}
public static <E extends Number> List<? super E> process(List<E> nums){
List<E> test = new ArrayList<E>();
return test;
}  

here is the compile error:

  Severity and DescriptionPathResourceLocationCreation TimeId
Type mismatch: cannot convert from List<String> to ArrayList<String>Java_CertifiacationGenericsTestEx.javaline 6118641014067121008
  

Could you please help me to understand where is the error exactly?
There is something wrong with my example or the book is wrong?
Many Thanks,

Haithem

[Haithem Jarraya]

I am sorry,
It was a mistake in the book:

  620....bug.......Q-16: method declaration s/b:
& 634
         public static <E extends Number> List<E> process(List<E> nums)  

Thanks for your many responses