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Generic Confusion

Prashant Kataria

Joined: Sep 16, 2006
Posts: 3
public static <E extends Number> List<? super E> process(List<E> num)

this is the method's signature.
i want to use method like this
//Insert cod here

which pair i should put at //Insert code here so that my code compile? at least is should accept input and output?

ArrayList<Integer> input=null;
ArrayList<Integer> output=null;

ArrayList<Integer> input=null;
List<Integer> output=null;

a. ArrayList<Integer> input=null;
List<Number> output=null;

b. List<Number> input=null;
ArrayList<Integer> output=null;

c. List<Number> input=null;
List<Number> output=null;

d. List<Integer> input=null;
List<Integer> output=null;

e. ArrayList<> input=null;
ArrayList<> output=null;

the answer in My book (SCJP 310-055 by Kathy Sierra and Bert Bates)
is b,e,f
but practically when i tested the code none of copiled.
please help to get answere
Barry Gaunt
Ranch Hand

Joined: Aug 03, 2002
Posts: 7729
That's correct - it does not compile for any of the choices. Please see the K & B errata for the correction to the question.

K & B errata
[ September 16, 2006: Message edited by: Barry Gaunt ]

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Prashant Kataria

Joined: Sep 16, 2006
Posts: 3
Thnaks for help.
I agree. Here's the link:
subject: Generic Confusion
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