public static int dot (Point v1s, Point v1e, Point v2s, Point v2e)
    {
        return ((v1e.x - v1s.x) * (v2e.x - v2s.x) + (v1e.y - v1s.y) * (v2e.y - v2s.y));
    }
public static int dot ( Point v1s , Point v1e , Point v2s , Point v2e ) { return ( ( v1e . x - v1s . x ) * ( v2e . x - v2s . x ) + ( v1e . y - v1s . y ) * ( v2e . y - v2s . y ) ) ; }
Computes and returns the dot product of the two vectors.

@param v1s the starting point of the first vector.
@param v1e the ending point of the first vector.
@param v2s the starting point of the second vector.
@param v2e the ending point of the second vector.