public static String generateRandomAlphanumericPassword(int length) {
        char[][] pairs = {{'a', 'z'}, {'A', 'Z'}, {'0', '9'}};
        RandomStringGenerator pwdGenerator = new RandomStringGenerator.Builder()
                .usingRandom(LazySecureRandom.INSTANCE::nextInt)
                .withinRange(pairs)
                .build();
        return pwdGenerator.generate(length);
    }
@Test
    public void testGenerateRandomAlphanumericPassword20() {
        assertThat(JOrphanUtils.generateRandomAlphanumericPassword(20), Matchers.matchesPattern("[A-Za-z0-9]{20}"));
    }