assertFalse(underlying.containsKey("b"));

    Iterator<String> keyIterator = keys.iterator();
    keyIterator.next();
    keyIterator.remove();
    assertFalse(underlying.containsKey("c"));

    Collection<String> values = map.values();
    values.remove("4");
    assertFalse(underlying.containsKey("d"));

    Iterator<String> valueIterator = values.iterator();
    valueIterator.next();
    valueIterator.remove();

     * @return An iterator of URL objects for the resources. If no resources are found, the iterator will be empty.
     *         Resources that the class loader does not have access to will not be included.
     * @see java.lang.ClassLoader#getResources(String)
     */
    public static Iterator<URL> getResources(final String name) {
        assertArgumentNotEmpty("name", name);

  /**
   * A sensible definition of {@link #firstEntry()} in terms of {@code entrySet().iterator()}.
   *
   * <p>If you override {@link #entrySet()}, you may wish to override {@link #firstEntry()} to
   * forward to this implementation.
   */
  protected @Nullable Entry<E> standardFirstEntry() {
    Iterator<Entry<E>> entryIterator = entrySet().iterator();
    if (!entryIterator.hasNext()) {
      return null;
    }

  }

  /**
   * A sensible definition of {@link #clear} in terms of the {@code iterator} method of {@link
   * #entrySet}. In many cases, you may wish to override {@link #clear} to forward to this
   * implementation.
   *
   * @since 7.0
   */
  protected void standardClear() {
    Iterators.clear(entrySet().iterator());
  }

  /**

    Iterator<List<Integer>> permutations = permutationSet.iterator();
    assertNextPermutation(Collections.<Integer>emptyList(), permutations);
    assertNoMorePermutations(permutations);
  }

  public void testPermutationSetOneElement() {
    Iterator<List<Integer>> permutations =
        Collections2.permutations(Collections.<Integer>singletonList(1)).iterator();

   */
  public static <E extends Enum<E>> EnumMultiset<E> create(Iterable<E> elements) {
    Iterator<E> iterator = elements.iterator();
    checkArgument(iterator.hasNext(), "EnumMultiset constructor passed empty Iterable");
    EnumMultiset<E> multiset = new EnumMultiset<>(iterator.next().getDeclaringClass());
    Iterables.addAll(multiset, elements);
    return multiset;
  }

  /**

        new Iterable<V>() {
          private boolean calledIteratorAlready = false;

          @Override
          public Iterator<V> iterator() {
            checkState(!calledIteratorAlready);
            calledIteratorAlready = true;
            return Iterators.forArray(v3());
          }
        };

    multimap().putAll(k3(), iterable);
  }

  @MapFeature.Require(SUPPORTS_PUT)

    KeySet(Map<K, Collection<V>> subMap) {
      super(subMap);
    }

    @Override
    public Iterator<K> iterator() {
      Iterator<Entry<K, Collection<V>>> entryIterator = map().entrySet().iterator();
      return new Iterator<K>() {
        @Nullable Entry<K, Collection<V>> entry;

        @Override
        public boolean hasNext() {
          return entryIterator.hasNext();

    Iterator<String> iterator = asList("a", "b", "a").iterator();
    Multiset<String> multiset = ImmutableMultiset.copyOf(iterator);
    assertEquals(HashMultiset.create(asList("a", "b", "a")), multiset);
  }

  public void testCopyOf_iteratorContainingNull() {
    Iterator<@Nullable String> iterator =
        Arrays.<@Nullable String>asList("a", null, "b").iterator();
    assertThrows(

  public void testRemovePresentConcurrentWithEntrySetIteration() {
    assertThrows(
        ConcurrentModificationException.class,
        () -> {
          Iterator<Entry<K, V>> iterator = getMap().entrySet().iterator();
          getMap().remove(k0());
          iterator.next();
        });
  }

  @MapFeature.Require({FAILS_FAST_ON_CONCURRENT_MODIFICATION, SUPPORTS_REMOVE})
  @CollectionSize.Require(SEVERAL)