void () { assertEquals("", StringUtil.join(List.of(), ",")); assertEquals("qqq", StringUtil.join(List.of("qqq"), ",")); assertEquals("", StringUtil.join(Collections.singletonList(null), ",")); assertEquals("a,b", StringUtil.join(List.of("a", "b"), ",")); assertEquals("foo,,bar", StringUtil.join(List.of("foo", "", "bar"), ",")); assertEquals("foo,,bar", StringUtil.join(new String[]{"foo", "", "bar"}, ",")); }