Iterator<String> iterator = asList("one", "two", "three", "four", "five").iterator();
    try {
      Iterators.getOnlyElement(iterator);
      fail();
    } catch (IllegalArgumentException expected) {
      assertThat(expected)
          .hasMessageThat()
          .isEqualTo("expected one element but was: <one, two, three, four, five>");
    }
  }

    Set<Object> zero = ImmutableSet.of();
    Set<Set<Object>> one = powerSet(zero);
    Set<Set<Set<Object>>> two = powerSet(one);
    Set<Set<Set<Set<Object>>>> four = powerSet(two);
    Set<Set<Set<Set<Set<Object>>>>> sixteen = powerSet(four);
    Set<Set<Set<Set<Set<Set<Object>>>>>> sixtyFiveThousandish = powerSet(sixteen);
    assertEquals(1 << 16, sixtyFiveThousandish.size());

    assertNull(map.get("four"));
    strings.add("four");
    assertEquals(ImmutableSortedMap.of("one", 3, "two", 3, "three", 5, "four", 4), map);
    assertEquals(Integer.valueOf(4), map.get("four"));
    SortedMap<String, Integer> headMap = map.headMap("two");
    assertEquals(ImmutableSortedMap.of("four", 4, "one", 3, "three", 5), headMap);
    strings.add("five");

    assertNull(map.get("four"));
    strings.add("four");
    assertEquals(ImmutableSortedMap.of("one", 3, "two", 3, "three", 5, "four", 4), map);
    assertEquals(Integer.valueOf(4), map.get("four"));
    SortedMap<String, Integer> headMap = map.headMap("two");
    assertEquals(ImmutableSortedMap.of("four", 4, "one", 3, "three", 5), headMap);
    strings.add("five");

   */
  @Override
  public String toString() {
    return super.toString();
  }

  /**
   * Returns the Java Unicode escape sequence for the given {@code char}, in the form "\u12AB" where
   * "12AB" is the four hexadecimal digits representing the 16-bit code unit.
   */
  private static String showCharacter(char c) {
    String hex = "0123456789ABCDEF";
    char[] tmp = {'\\', 'u', '\0', '\0', '\0', '\0'};

    abstract Equivalence<Object> defaultEquivalence();
  }

  /**
   * A helper object for operating on {@link InternalEntry} instances in a type-safe and efficient
   * manner.
   *
   * <p>For each of the four combinations of strong/weak key and strong/weak value, there are
   * corresponding {@link InternalEntry}, {@link Segment}, and {@link InternalEntryHelper}
   * implementations.
   *

    Iterator<String> iterator = asList("one", "two", "three", "four", "five").iterator();
    try {
      Iterators.getOnlyElement(iterator);
      fail();
    } catch (IllegalArgumentException expected) {
      assertThat(expected)
          .hasMessageThat()
          .isEqualTo("expected one element but was: <one, two, three, four, five>");
    }
  }

   */
  @Override
  public String toString() {
    return super.toString();
  }

  /**
   * Returns the Java Unicode escape sequence for the given {@code char}, in the form "\u12AB" where
   * "12AB" is the four hexadecimal digits representing the 16-bit code unit.
   */
  private static String showCharacter(char c) {
    String hex = "0123456789ABCDEF";
    char[] tmp = {'\\', 'u', '\0', '\0', '\0', '\0'};

    checkNotNull(a);
    checkNotNull(b);
    checkNotNull(c);
    return concat(consumingForArray(a, b, c));
  }

  /**
   * Combines four iterators into a single iterator. The returned iterator iterates across the
   * elements in {@code a}, followed by the elements in {@code b}, followed by the elements in

    checkNotNull(a);
    checkNotNull(b);
    checkNotNull(c);
    return concat(consumingForArray(a, b, c));
  }

  /**
   * Combines four iterators into a single iterator. The returned iterator iterates across the
   * elements in {@code a}, followed by the elements in {@code b}, followed by the elements in