@Test
public void join() {

    Assert.assertEquals(CommonUtils.join(null, ","), "");
    Assert.assertEquals(CommonUtils.join(new ArrayList(), ","), "");
    List<String> s = new ArrayList<String>();
    s.add("a");
    s.add("b");
    s.add("c");
    Assert.assertEquals(CommonUtils.join(s, "1"), "a1b1c");
}