return size;
  }

  private abstract static class BiIterator<
          K extends @Nullable Object, V extends @Nullable Object, T extends @Nullable Object>
      implements Iterator<T> {
    final HashBiMap<K, V> biMap;

    @Nullable Node<K, V> next;
    @Nullable Node<K, V> toRemove;
    int expectedModCount;
    int remaining;

    BiIterator(HashBiMap<K, V> biMap) {
      this.biMap = biMap;

  }

  public void testSize1() {
    Iterator<Integer> iterator = singleton(0).iterator();
    assertEquals(1, Iterators.size(iterator));
  }

  public void testSize_partiallyConsumed() {
    Iterator<Integer> iterator = asList(1, 2, 3, 4, 5).iterator();
    iterator.next();
    iterator.next();
    assertEquals(3, Iterators.size(iterator));
  }

import java.util.Collections;
import java.util.Iterator;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * A utility for testing an Iterator implementation by comparing its behavior to that of a "known
 * good" reference implementation. In order to accomplish this, it's important to test a great
 * variety of sequences of the {@link Iterator#next}, {@link Iterator#hasNext} and {@link

    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 void testCopyOf_iterator_empty() {
    Iterator<String> iterator = emptyIterator();
    Set<String> set = copyOf(iterator);
    assertEquals(Collections.<String>emptySet(), set);
    assertThat(set).isSameInstanceAs(this.<String>of());
  }

  public void testCopyOf_iterator_oneElement() {
    Iterator<String> iterator = singletonIterator("a");
    Set<String> set = copyOf(iterator);
    assertEquals(singleton("a"), set);
  }

        @Override
        @Nullable N visitNext(Deque<Iterator<? extends N>> horizon) {
          Iterator<? extends N> top = horizon.getFirst();
          if (top.hasNext()) {
            return checkNotNull(top.next());
          }
          horizon.removeFirst();
          return null;
        }
      };
    }

    final Iterator<N> breadthFirst(Iterator<? extends N> startNodes) {

    FluentIterable<Integer> cycle = fluent(1, 2).cycle();
    Iterator<Integer> iterator = cycle.iterator();
    iterator.next();
    iterator.remove();
    iterator.next();
    iterator.remove();
    assertFalse(iterator.hasNext());
    assertFalse(cycle.iterator().hasNext());
  }

  public void testAppend() {
    FluentIterable<Integer> result =

    assertThat(j.join(ImmutableMultimap.of("", "").entries())).isEqualTo(":");
    assertThat(j.join(ImmutableMultimap.of("", "").entries().iterator())).isEqualTo(":");
    assertThat(j.join(ImmutableMultimap.of("1", "a", "1", "b").entries())).isEqualTo("1:a;1:b");
    assertThat(j.join(ImmutableMultimap.of("1", "a", "1", "b").entries().iterator()))
        .isEqualTo("1:a;1:b");

    Iterator<Integer> iter =
        new AbstractIterator<Integer>() {
          @Override
          public Integer computeNext() {
            endOfData();
            throw new SomeUncheckedException();
          }
        };
    assertThrows(SomeUncheckedException.class, iter::hasNext);
  }

  public void testCantRemove() {
    Iterator<Integer> iter =

  }

  public void testCopyOf_iterator_general() {
    Iterator<String> iterator = asList("a", "b", "a").iterator();
    Multiset<String> multiset = ImmutableSortedMultiset.copyOf(iterator);
    assertEquals(HashMultiset.create(asList("a", "b", "a")), multiset);
  }

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