What is the time complexity of java.util.Collections.sort() method?

Question

I have written the following class:

public class SortingObjectsWithAngleField implements Comparator {  
    public int compare(Point p1, Point p         


        

Answer 1

You could have read up the docs on Collections sort, but here it is for you:

The sorting algorithm is a modified mergesort (in which the merge is omitted if the highest element in the low sublist is less than the lowest element in the high sublist). This algorithm offers guaranteed n log(n) performance.

Your Comparator doesn't change this complexity, unless you do anything with loops over your collection in it, which you don't.

Answer 2

Everyone has stated the API doc, adding some more relevant information which I found.

If you provide custom comparator, then a modified version of mergesort (also known as timsort) is used. The implementation has been borrowed from list sort for python.

In the best case as few as n-1 comparisons are needed, so best case is O(n) and guaranteed performance in all the cases is O(n.lg(n))

Answer 3

Taken from Collections.sort -

The sorting algorithm is a modified mergesort (in which the merge is omitted if the highest element in the low sublist is less than the lowest element in the high sublist). This algorithm offers guaranteed n*log(n) performance

Answer 4

You should have found it in the API: n log(n).