public static boolean isEmpty(ProviderGroup group) {
        return group == null || group.isEmpty();
    }
@Test
    public void isEmpty() throws Exception {
        ProviderGroup pg = null;
        Assert.assertTrue(ProviderHelper.isEmpty(pg));

        pg = new ProviderGroup("xxx", null);
        Assert.assertTrue(ProviderHelper.isEmpty(pg));

        pg = new ProviderGroup("xxx", new ArrayList<ProviderInfo>());
        Assert.assertTrue(ProviderHelper.isEmpty(pg));

        pg.add(ProviderHelper.toProviderInfo("127.0.0.1:12200"));
        Assert.assertFalse(ProviderHelper.isEmpty(pg));
    }