Max points on a line

Given n points on a 2D plane, find the maximum number of points that lie on the same straight line.

public int maxPoints(Point[] points) {
    if(points == null || points.length == 0) return 0;
 
    HashMap<Double, Integer> result = new HashMap<Double, Integer>();
    int max=0;
 
    for(int i=0; i<points.length; i++){
        int duplicate = 1;//
        int vertical = 0;
        for(int j=i+1; j < points.length; j++){
            //handle duplicates and vertical
            if(points[i].x == points[j].x){
                if(points[i].y == points[j].y){
                    duplicate++;
                }else{
                    vertical++;
                }
            }else{
                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(result.get(slope) != null){
                    result.put(slope, result.get(slope) + 1);
                }else{
                    result.put(slope, 1);
                }
            }
        }
 
        for(Integer count: result.values()){
            if(count+duplicate > max){
                max = count+duplicate;
            }
        }
 
        max = Math.max(vertical + duplicate, max);
        result.clear();
    }
 
 
    return max;
}