Sort array in Java

Question

What happened if I sort a Java array with criteria based on its element?

Point[] points = new Point[10];
Arrays.sort(temp, points[0].SLOPE_ORDER);

Will this be a recursive call?

SLOPE_ORDER is a comparator:

public final Comparator<Point> SLOPE_ORDER = new SlopeOrder();       // YOUR DEFINITION HERE

private class SlopeOrder implements Comparator<Point>
{
    public int compare(Point p1, Point p2)
    {
         ...
    }
}

Would it make a difference whether the sorting is recursive or not? Every recursion can be written as an iteration. Applying the blackbox principle that means: "Arrays.sort()" is working. IF this question is in the scope of homework like "Apply a recursive sorting algorithm" that answer is for sure not, what is expected. — dognose
– dognose, Commented Apr 29, 2014 at 22:42
SLOPE_ORDER should be a comparator function. It will be called each time the algorithm needs to compare two elements. — Troveldom
– Troveldom, Commented Apr 29, 2014 at 22:44
The big question is, why do you need to know if it will be a recursive call? — Troveldom
– Troveldom, Commented Apr 29, 2014 at 22:48

peter.petrov · Accepted Answer · 2014-04-29 22:44:28Z

4

See here:

Arrays.sort

Implementation note: This implementation is a stable, adaptive, iterative mergesort that requires far fewer than n lg(n) comparisons when the input array is partially sorted, while offering the performance of a traditional mergesort when the input array is randomly ordered. If the input array is nearly sorted, the implementation requires approximately n comparisons. Temporary storage requirements vary from a small constant for nearly sorted input arrays to n/2 object references for randomly ordered input arrays.

So the answer is: no, it's not recursive.

answered Apr 29, 2014 at 22:44

peter.petrov

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toniedzwiedz · Accepted Answer · 2014-04-29 22:53:06Z

1

Judging by the naming convention and the contract of Array#sort, SLOPE_ORDER is a static final member of the Point class that you are using. Specifically, it's a comparator that can be passed to the sort method.

To answer your question, nothing interesting will happen.

Arrays.sort(temp, points[0].SLOPE_ORDER);

will evaluate points[0].SLOPE_ORDER as the reference to the object and use its value as an argument to perform the sorting without needing to look at points[0] ever again (at least not in order to get SLOPE_ORDER.

If SLOPE_ORDER is both static and final, this can be replaced with

Arrays.sort(temp, Point.SLOPE_ORDER);

the result will be exactly the same and the code is much easier to understand.

answered Apr 29, 2014 at 22:53

toniedzwiedz

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