How to call this generic function?

Question

I have tried many ways to call the countGreaterThan() function (described here), but I am unable to get it to work. I understand I need to use Integer instances and not primitives. This is what I've tried:

MainClass.java

public class MainClass {

public static <T extends Comparable<T>> int countGreaterThan(T[] anArray, T elem) {
    int count = 0;
    for (T e : anArray)
        if (e.compareTo(elem) > 0)
            ++count;
    return count;
}

public static void main(String[] args){
    Integer[] myArray = {0,1,2,3,4};
    Integer myInt = new Integer(2);
    int result = countGreaterThan(myArray,myInt);
            System.out.println(result);
}
}

This is the interface Comparable.java

public interface Comparable<T> {
   public int compareTo(T o);
}

And this is the error I get -

Bound mismatch: The generic method countGreatherThan(T[],T) of type MainClass is not applicable for the arguments(Integer[],Integer). The inferred type Integer is not a valid subsitute for the bounded parameter >

You should definitely show us countGreaterThan method, or at least it's signature, so we know what type it returns (if any) and what it does in it's body. — , Jun 28 '14 at 18:18

score 1 · Answer 1 · answered Jun 28 '14 at 17:44

1

If I understand your question, it appears like you are calling countGreaterThan()! What you aren't doing is printing the result, or saving the result.

countGreaterThan(myArray,myInt);

Should be

int result = countGreaterThan(myArray, myInt);
System.out.println(result);

answered Jun 28 '14 at 17:44

Elliott Frisch

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@HovercraftFullOfEels I actually ran the code. It's fine. – Elliott Frisch Jun 28 '14 at 17:47
The method is in the link in the original post. – user3745246 Jun 28 '14 at 18:43
The real problem is that it doesn't compile. – user3745246 Jun 28 '14 at 18:43
Yes, the one at the bottom of that link does. – Elliott Frisch Jun 28 '14 at 18:44
I've tried to compile using your 2 lines of code but it didn't work either. I still get this error http://gyazo.com/8d9cbba14b91d8758d670eecb16b65c3 – user3745246 Jun 28 '14 at 19:34
There are 3 of my replies before this comment, including a screenshot, what should I add more ? – user3745246 Jun 28 '14 at 20:12
I edited 1st post, check it now and tell me if it's ok this time. – user3745246 Jun 28 '14 at 20:35
@user3745246: much better, thank you! 1+ up-vote. Vote to close retracted. – Hovercraft Full Of Eels Jun 28 '14 at 21:06
My bad. 1+ to your answer. – Hovercraft Full Of Eels Jun 28 '14 at 21:10

score 1 · Accepted Answer · answered Jun 28 '14 at 21:08

1

I have to wonder if you've created your own Comparable.java interface and are using it. If so, you're seeing your error because Integer is not using your interface, but rather the one that is part of core Java. If so, get rid of your Comparable.java class, delete it, and just use the one that is part of core Java. No need to import as it is part of the java.lang package, a package whose classes are all automatically imported by default.

answered Jun 28 '14 at 21:08

Hovercraft Full Of Eels

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@user3745246: Sorry for annoying you to improve your question, but note that we could only figure this out after you did your improvents. Thanks for the improvements and you're welcome for the answer. – Hovercraft Full Of Eels Jun 28 '14 at 21:17

How to call this generic function?

2 Answers2