public double nextDouble() {
        return real.nextDouble();
    }
@Test
    public void testRandom_double_double() {
        System.out.println("nextDouble");
        double lo = -10.0;
        double hi = 20.0;
        smile.math.Random instance = new Random(System.currentTimeMillis());
        for (int i = 0; i < 1000000; i++) {
            double result = instance.nextDouble(lo, hi);
            assertTrue(result >= lo);
            assertTrue(result < hi);
        }
    }