Max Points on a Line

/**
 *Max Points on a Line Total Accepted: 13921 Total Submissions: 130280 My Submissions
 *Given n points on a 2D plane, find the maximum number of points that lie on the same straight line.
 */
 
 /**
 * Definition for a point.
 * class Point {
 *     int x;
 *     int y;
 *     Point() { x = 0; y = 0; }
 *     Point(int a, int b) { x = a; y = b; }
 * }
 */
public class Solution {
    public int maxPoints(Point[] points) {
       int maxLine = 0;
    Map<String, Integer> pointCounts = new HashMap<String, Integer>();
        for (int i=0; i<(points.length); i++) {
            int coincident = 0;
            pointCounts.clear();
            for (int j=i+1; j<points.length; j++) {
                String slope;
                if (points[i].x==points[j].x && points[i].y==points[j].y) {
                    coincident++;
                    continue;
                } else if (points[i].x == points[j].x) {
                    slope = "N";
                } else if (points[i].y == points[j].y) {
                    slope = "0,0"; // logically we don't need this, but in practice i find that we do
                } else {
                        slope=slopeToString((points[i].y-points[j].y),(points[i].x                         -points[j].x));
                }

                if (pointCounts.containsKey(slope))
                    pointCounts.put(slope, pointCounts.get(slope)+1);
                else
                    pointCounts.put(slope, new Integer(1));
            }//end for
            maxLine = Math.max(maxLine, 1+coincident+maxValue(pointCounts));
        }// end for

        return maxLine;
    }
    
    private int maxValue(Map<String, Integer> StringIntMap) {
        int max = 0;
        Set<String> keys = StringIntMap.keySet();
        Iterator iter = keys.iterator();
        while (iter.hasNext())
        max = Math.max(max, StringIntMap.get(iter.next()));
        return max;
    }
    
    private String slopeToString(int x ,int y)
    {
        int r=gcd(x,y);
        x=x/r;
        y=x/r;
        String aa=x+","+y;
        return aa;
    }
    int gcd(int m,int n)
    {
        if (m % n == 0)
        {return n;}
        else
        {return gcd(n,m % n);}
    }
}