[LeetCode] Max Points on a Line

Problem:
Given n points on a 2D plane, find the maximum number of points that lie on the same straight line.
Solution:O(n*n)

public class Solution {
   public int maxPoints(Point[] points) {

      Map<Double, Integer> map = new HashMap<>();

      int ret = 0;

      int size = points.length;

      for (int i = 0; i < size; i++) {

         int invalidK = 0;

         int add = 1;

         for (int j = i + 1; j < size; j++) {

            if (points[j].x == points[i].x) {

               if (points[j].y == points[i].y) {

                  add++;

               } else {

                  invalidK++;

               }

               continue;

            }

            double slope = points[j].y == points[i].y ? 0.0: (1.0 * (points[j].y - points[i].y))/ (points[j].x - points[i].x);
     if (map.containsKey(slope)) {

               int count = map.get(slope);
        map.put(slope, count + 1);
     } else {
        map.put(slope, 1);
     }

         }

         for (Integer it : map.values()) {

            ret = Math.max(it.intValue() + add, ret);

         }

         ret = Math.max(invalidK + add, ret);

         map.clear();

      }
      return ret;

   }
}