@Test
public void testJoinCollectionString() throws Exception {

    List<String> list = new ArrayList<String>();
    assertEquals("", StringUtils.join(list, ","));
    list.add("v1");
    assertEquals("v1", StringUtils.join(list, "-"));
    list.add("v2");
    list.add("v3");
    String out = StringUtils.join(list, ":");
    assertEquals("v1:v2:v3", out);
}