Java - Generics with statics

Question

stuck on something that should be pretty simple.

I have the class TreeSort:

public class TreeSort {

    public static <E extends Comparable<? super E>> void sort(E[] nums) {
        //Sorting
    }
}

And a simple Tester class with a main method for testing:

public class Tester {
    public static void main(String[] args) throws TreeStructureException {

        int[] nums = { 11, 2, 8, 30, 12, 21, 6, 4, 3, 18 };
        TreeSort.sort(nums); // The method sort(E[]) in the type TreeSort is not 
                             // applicable for the arguments (int[])
    }

}

Why do I get this error? Thanks all

Because an int[] isn't an Integer[].

Dave Newton
– Dave Newton

2014-05-02 17:04:46 +00:00
Commented May 2, 2014 at 17:04 — Dave Newton
– Dave Newton, Commented May 2, 2014 at 17:04

Luiggi Mendoza · Accepted Answer · 2014-05-02 17:05:40Z

3

int[] nums is an Object. You have two ways to solve this:

Change the variable to Integer[].
Create an additional method to support int[].

In case you're not doing this for homework/exercise/specific sort algorithm purpose, use Arrays#sort(int[]) or Arrays#sort(Object[] array) instead.

answered May 2, 2014 at 17:05

Luiggi Mendoza

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1 Comment

zZShort_CircuitZz Over a year ago

Thanks, that was the ticket. Needed to use Integer[]

evanchooly · Accepted Answer · 2014-05-02 17:03:37Z

2

Primitives and generics aren't really compatible. You'll either need a Integer[] (gross) or sort should take a int[].

answered May 2, 2014 at 17:03

evanchooly

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3 Comments

NWard Over a year ago

What's gross about Integer[]?

Mike B Over a year ago

@NWard The memory overhead from boxing, loss of memory locality when traversing the array, and an extra pointer dereference for each element accessed mainly.

zZShort_CircuitZz Over a year ago

You're correct, needed to change int[] to Integer[]

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