public static double distance(int[] a, int[] b) {
        return sqrt(squaredDistance(a, b));
    }
@Test
    public void testDistance_doubleArr_doubleArr() {
        System.out.println("distance");
        double[] x = {-2.1968219, -0.9559913, -0.0431738, 1.0567679, 0.3853515};
        double[] y = {-1.7781325, -0.6659839, 0.9526148, -0.9460919, -0.3925300};
        assertEquals(2.422302, MathEx.distance(x, y), 1E-6);
    }