public class ClosestPoints {

    public static double distanceSquare(double[] point1, double[] point2) {
        return (point1[0] - point2[0]) * (point1[0] - point2[0])
                + (point1[1] - point2[1]) * (point1[1] - point2[1]);
    }

    public static void main(String[] args) {

        double[][] points = { { -1, 3 }, { -1, -1 }, { 1, 1 }, { 2, 0.5 },
                { 2, -1 }, { 3, 3 }, { 4, 2 }, { 4, -0.5 } };

        double minDistance = distanceSquare(points[0], points[1]);
        int p1 = 0, p2 = 1;
        for (int i = 0; i < points.length; ++i)
            for (int j = i + 1; j < points.length; ++j) {
                double distance = distanceSquare(points[i], points[j]);
                if (distance < minDistance) {
                    p1 = i;
                    p2 = j;
                    minDistance = distance;
                }
            }

        System.out.printf("The closest points are Point %d and Point %d with distance %f\n",
            p1, p2, Math.sqrt(minDistance));
    }

}