What's the sort order of Java's Collections.sort(list, comparator)? small to big or big to small?

Question

Apparently, it\'s not documented or I missed it.

Here\'s the link to the documentation and below\'s the text as an image:

EDIT(17/5): I think to

Answer 1

The documentation of Comparator.compareTo(o1, o2) method says

Compares its two arguments for order. Returns a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second.

So if you want to sort from natural ordering , that is small to big, then you should write the implementation as defined in the documentation

public int compareTo(Integer o1, Integer o2) {
     int v1 = (o1);
     int v2 = (o2);
     if(v1 == v2) {
        return 0;
     }
     if(v1 < v2) {
        return -1; //return negative integer if first argument is less than second
     }
     return 1;
}

If you want the sorting to be in reverse order, that is big to small

public int compareTo(Integer o1, Integer o2) {
     int v1 = (o1);
     int v2 = (o2);
     if(v1 == v2) {
        return 0;
     }
     if(v1 < v2) {
        return 1;  //do the other way
     }
     return -1;
}