@Override
    public double entropy() {
        return entropy;
    }
@Test
    public void testEntropy() {
        System.out.println("entropy");
        GaussianDistribution instance = new GaussianDistribution(0.0, 1.0);
        instance.rand();
        assertEquals(1.418939, instance.entropy(), 1E-6);
        instance = new GaussianDistribution(1.0, 2.0);
        instance.rand();
        assertEquals(2.112086, instance.entropy(), 1E-6);
        instance = new GaussianDistribution(2.0, 0.5);
        instance.rand();
        assertEquals(0.7257914, instance.entropy(), 1E-6);
        instance = new GaussianDistribution(3.0, 3.8);
        instance.rand();
        assertEquals(2.753940, instance.entropy(), 1E-6);
    }