public double d(int[] x, int[] y) {
        if (x.length != y.length)
            throw new IllegalArgumentException(String.format("Arrays have different length: x[%d], y[%d]", x.length, y.length));

        double dist = 0.0;

        if (weight == null) {
            for (int i = 0; i < x.length; i++) {
                dist += Math.abs(x[i] - y[i]);
            }
        } else {
            if (x.length != weight.length)
                throw new IllegalArgumentException(String.format("Input vectors and weight vector have different length: %d, %d", x.length, weight.length));

            for (int i = 0; i < x.length; i++) {
                dist += weight[i] * Math.abs(x[i] - y[i]);
            }
        }

        return dist;
    }
@Test
    public void testDistanceDouble() {
        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(4.485227, new ManhattanDistance().d(x, y), 1E-6);
    }