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Generics Question from K&B Study Guide.

 
Greenhorn
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The following is part of a question from the K&B study guide.

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;



Answer A shown above was stated as being incorrect as 'The return type of process is definitely declared as a List, not an ArrayList'. The above confused me so I tried out the following code which seemed to compile fine. So is the answer above correct or (more likely) am I confused.



Thanks
Tom
 
Tom Scott
Greenhorn
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Gah - sorry all spent ages on this, now I see i missed the call to process()
 
Tom Scott
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And looking at the compiler message I now see that the return type is a List<> and therefore does not 'fit' in an ArrayList<> reference.

Cheers
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