public boolean isEmpty() {
        return CommonUtils.isEmpty(providerInfos);
    }
@Test
    public void isEmpty() throws Exception {
        ProviderGroup pg = new ProviderGroup("xxx", null);
        Assert.assertTrue(pg.isEmpty());

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

        pg = new ProviderGroup("xxx", Arrays.asList(ProviderHelper.toProviderInfo("127.0.0.1:12200")));
        Assert.assertTrue(!pg.isEmpty());
    }