@Override
          public Iterator<Entry<Range<K>, V>> iterator() {
            return entryIterator();
          }

          @Override
          public boolean retainAll(Collection<?> c) {
            return removeEntryIf(not(in(c)));
          }

          @Override
          public int size() {
            return Iterators.size(iterator());
          }

          @Override

    Iterator<String> iterator = list.iterator();
    assertTrue(iterator.hasNext());
    assertEquals("1", iterator.next());
    assertTrue(iterator.hasNext());
    assertEquals("2", iterator.next());
    assertTrue(iterator.hasNext());
    assertEquals("3", iterator.next());
    assertTrue(iterator.hasNext());
    assertEquals("4", iterator.next());
    assertFalse(iterator.hasNext());

  }

  static <T extends @Nullable Object> Iterator<T> cycle(Iterable<T> iterable) {
    return new Iterator<T>() {
      Iterator<T> iterator = Collections.<T>emptySet().iterator();

      @Override
      public boolean hasNext() {
        return true;
      }

      @Override
      public T next() {
        if (!iterator.hasNext()) {
          iterator = iterable.iterator();
        }

     */
    public IteratorEnumeration(final Iterator<T> iterator) {
        assertArgumentNotNull("iterator", iterator);
        this.iterator = iterator;
    }

    /**
     * {@link IteratorEnumeration}を作成します。
     *
     * @param iterable
     *            反復可能なオブジェクト。{@literal null}であってはいけません
     */
    public IteratorEnumeration(final Iterable<T> iterable) {
        assertArgumentNotNull("iterable", iterable);

  }

  public void testCopyOf_iterator_oneElementRepeated() {
    Iterator<String> iterator = Iterators.forArray("a", "a", "a");
    Set<String> set = copyOf(iterator);
    assertEquals(Collections.singleton("a"), set);
  }

  public void testCopyOf_iterator_general() {
    Iterator<String> iterator = Iterators.forArray("a", "b", "a");
    Set<String> set = copyOf(iterator);
    assertEquals(2, set.size());

  }

  public void testCopyOf_iterator_oneElementRepeated() {
    Iterator<String> iterator = Iterators.forArray("a", "a", "a");
    Set<String> set = copyOf(iterator);
    assertEquals(Collections.singleton("a"), set);
  }

  public void testCopyOf_iterator_general() {
    Iterator<String> iterator = Iterators.forArray("a", "b", "a");
    Set<String> set = copyOf(iterator);
    assertEquals(2, set.size());

    }
  }

  public void testCopyOf_iterator_empty() {
    Iterator<String> iterator = Iterators.emptyIterator();
    Multiset<String> multiset = ImmutableMultiset.copyOf(iterator);
    assertTrue(multiset.isEmpty());
  }

  public void testCopyOf_iterator_oneElement() {
    Iterator<String> iterator = Iterators.singletonIterator("a");

      @Override
      protected Iterator<Integer> newTargetIterator() {
        return newDoubler(1, 2);
      }
    }.test();
  }

  public void testDoubler() {
    Iterable<Integer> doubled =
        new Iterable<Integer>() {
          @Override
          public Iterator<Integer> iterator() {
            return newDoubler(2, 32);
          }
        };

    Iterator<Integer> iterator = ints.iterator();
    assertEquals(0, (int) numberOrdering.min(iterator));
    assertFalse(iterator.hasNext());
  }

  public void testIteratorMaxExhaustsIterator() {
    List<Integer> ints = Lists.newArrayList(9, 0, 3, 5);
    Iterator<Integer> iterator = ints.iterator();
    assertEquals(9, (int) numberOrdering.max(iterator));
    assertFalse(iterator.hasNext());

    Iterator<Integer> iterator = ints.iterator();
    assertEquals(0, (int) numberOrdering.min(iterator));
    assertFalse(iterator.hasNext());
  }

  public void testIteratorMaxExhaustsIterator() {
    List<Integer> ints = Lists.newArrayList(9, 0, 3, 5);
    Iterator<Integer> iterator = ints.iterator();
    assertEquals(9, (int) numberOrdering.max(iterator));
    assertFalse(iterator.hasNext());