public static int rand(int min, int max) {
        return RANDOM.nextInt(max) % (max - min + 1) + min;
    }
@Test
    public void testRand() {
        Assert.assertEquals(8, StringKit.rand(8).length());
        Assert.assertEquals(10, StringKit.rand(10).length());

        for (int i = 0; i < 100; i++) {
            int num = StringKit.rand(1, 10);
            Assert.assertTrue(num < 11);
            Assert.assertTrue(num > 0);
        }
    }