### Question:
StringUtil { public static String join(Collection strings, String sep) { return join(strings.iterator(), sep); }  static String join(Collection strings, String sep); static String join(Iterator strings, String sep); static String padding(int width); static boolean isBlank(String string); static boolean isNumeric(String string); static String normaliseWhitespace(String string);  }### Answer:
@Test public void join() { assertEquals("", StringUtil.join(Arrays.<String>asList(""), " ")); assertEquals("one", StringUtil.join(Arrays.<String>asList("one"), " ")); assertEquals("one two three", StringUtil.join(Arrays.<String>asList("one", "two", "three"), " ")); }