在Java中对整数进行排序会首先返回负数吗？

Question

I have a comparator like so:

Collections.sort( sortedPlayers, new Comparator<RoundPlayer>()
{
    public int compare(RoundPlayer p1, RoundPlayer p2)
    {
        return p1.getScore() - p2.getScore();
    }
});

Sorted players is a list of player objects, the scores they return are ints such as, 200, -300, 1000 etc.

The goal of the comparator is to sort them so they are descending order, 1000, 200, -300.

However this comparator seems to return erratic results. Often with negative numbers coming out first.

Answer 1

Just reverse your return value you currently have

sample

return p2.getScore() - p1.getScore(); //will sort in descending order

Answer 2

If you want to sort by descending order then consider wrapping your Comparator using Collections.reverseOrder(Comparator cmp) .

Also note that subtracting the two values is a bad idea because of integer overflow. Your compare logic is p1.getScore() - p2.getScore() . Consider p1.score = 2147483647, p2.score = -2147483648, your comparator would return -1, incorrectly indicating p1's score is less than p2's score.

The correct logic is to test for <, = and >, returning -1, 0 and 1. Better yet, Integer already implements this logic so you can simply delegate to its compareTo method.

return Integer.valueOf(p1.getScore()).compareTo(Integer.valueOf(p2.getScore());