When I run this repository, I figure out this small bug.

Can I add a small change like below?

public class HeapSort {
// Driver program
public static void main(String args[]) {
int arr[] = {12, 11, 13, 5, 6, 7};

    **heap_sort ob = new heap_sort();**
    ob.sort(arr);

    System.out.println("Sorted array is");
    printArray(arr);
}

}