checkNotNull(separator);
    if (array.length == 0) {
      return "";
    }

    // For pre-sizing a builder, just get the right order of magnitude
    StringBuilder builder = new StringBuilder(array.length * 12);
    builder.append(array[0]);
    for (int i = 1; i < array.length; i++) {
      builder.append(separator).append(array[i]);
    }
    return builder.toString();
  }

  /**

        multimap.putAll("foo", asList(6));
        multimap.putAll("baz", asList(7, 8));
        multimap.putAll("dog", asList(9));
        multimap.putAll("bar", asList(10, 11));
        multimap.putAll("cat", asList(12, 13, 14));
        return multimap.keySet().iterator();
      }

      @Override
      protected void verify(List<String> elements) {
        assertEquals(newHashSet(elements), multimap.keySet());
      }

    assertEquals("yh", is('a').replaceFrom("yaha", ""));
    assertEquals("yoho", is('a').replaceFrom("yaha", "o"));
    assertEquals("yoohoo", is('a').replaceFrom("yaha", "oo"));
    assertEquals("12 > 5", is('>').replaceFrom("12 > 5", ">"));
  }

  public void testRetainFrom() {
    assertEquals("aaa", is('a').retainFrom("bazaar"));
    assertEquals("z", is('z').retainFrom("bazaar"));

    assertEquals("yh", is('a').replaceFrom("yaha", ""));
    assertEquals("yoho", is('a').replaceFrom("yaha", "o"));
    assertEquals("yoohoo", is('a').replaceFrom("yaha", "oo"));
    assertEquals("12 > 5", is('>').replaceFrom("12 > 5", ">"));
  }

  public void testRetainFrom() {
    assertEquals("aaa", is('a').retainFrom("bazaar"));
    assertEquals("z", is('z').retainFrom("bazaar"));

      E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10, E e11, E e12, E... others) {
    checkArgument(
        others.length <= Integer.MAX_VALUE - 12, "the total number of elements must fit in an int");
    Object[] array = new Object[12 + others.length];
    array[0] = e1;
    array[1] = e2;
    array[2] = e3;
    array[3] = e4;
    array[4] = e5;
    array[5] = e6;
    array[6] = e7;

    a = ImmutableList.of(4, 8, 15, 16, 23, 42);
    b = asList(4, 8, 15, 16, 23, 42);
    assertTrue(Iterators.elementsEqual(a.iterator(), b.iterator()));

    // An element differs.
    a = asList(4, 8, 15, 12, 23, 42);
    b = asList(4, 8, 15, 16, 23, 42);
    assertFalse(Iterators.elementsEqual(a.iterator(), b.iterator()));

    // null versus non-null.
    a = Arrays.<@Nullable Integer>asList(4, 8, 15, null, 23, 42);

        new ImmutableSortedSet.Builder<Integer>(TO_STRING).add(3, 12, 101, 44).build();
    assertThat(set).containsExactly(101, 12, 3, 44).inOrder();
  }

  public void testSupertypeComparatorSubtypeElements() {
    SortedSet<Number> set =
        new ImmutableSortedSet.Builder<Number>(TO_STRING).add(3, 12, 101, 44).build();
    assertThat(set).containsExactly(101, 12, 3, 44).inOrder();
  }

  @Override

    Helpers.testComparator(arbitrary, list);
  }

  public void testUsingToString() {
    Ordering<Object> ordering = Ordering.usingToString();
    Helpers.testComparator(ordering, 1, 12, 124, 2);
    assertEquals("Ordering.usingToString()", ordering.toString());
    assertSame(ordering, reserialize(ordering));
  }

  // use an enum to get easy serializability

    Helpers.testComparator(arbitrary, list);
  }

  public void testUsingToString() {
    Ordering<Object> ordering = Ordering.usingToString();
    Helpers.testComparator(ordering, 1, 12, 124, 2);
    assertEquals("Ordering.usingToString()", ordering.toString());
    assertSame(ordering, reserialize(ordering));
  }

  // use an enum to get easy serializability

    assertEquals(
        InetAddresses.fromLittleEndianByteArray(
            new byte[] {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16}),
        InetAddress.getByAddress(
            new byte[] {16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1}));

    assertThrows(
        UnknownHostException.class, () -> InetAddresses.fromLittleEndianByteArray(new byte[3]));
  }