I have a two dimensional euclidean space. Three points are given.
For example (p2 is the middle point):
Point2D p1 = new Point2D.Double(177, 289); Po
From the wiki you referenced, the curvature is defined as
where A is the area enclosed by the triangle formed by the three points, x, y and z (p1, p2, p3 in your case) and |x-y| is the distance between points x and y.
Translate the formula to code and you're done!