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

Question

I have written the following class:

public class SortingObjectsWithAngleField implements Comparator<Point> {  
    public int compare(Point p1, Point p2) {
        double delta = p1.getAngle() - p2.getAngle();
        if(delta == 0.00001)
            return 0;
        return (delta > 0.00001) ? 1 : -1;
    }
}

Then, in my main() method, I have created a List to which I add some objects which has "X" and "angle" field.

I then use:

Collections.sort(list, new SortingObjectsWithAngleField());

What is the complexity of this sort method?

Answer 1

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

This algorithm offers guaranteed n log(n) performance.

Answer 2

您应该在 API 中找到它： n log(n)<\/a> 。

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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

Everyone has stated the API doc<\/a> , adding some more relevant information which I found.

The implementation has been borrowed from