StorageUtils { public static String createCompositeId(String... pieces) { return Arrays.stream(pieces).collect(Collectors.joining(COMPOSITE_ID_DELIMITER)); }  static String createCompositeId(String... pieces); static String[] parseCompositeId(String id, int requiredSize);  }
@Test public void testCreateCompositeId() { assertThat(createCompositeId("1", "2", "3"), equalTo("1:2:3")); }