}

    void setValue(@ParametricNullness V value) {
      checkState(current != null);
      current.value = value;
    }
  }

  /** An {@code Iterator} over distinct keys in key head order. */
  private class DistinctKeyIterator implements Iterator<K> {
    final Set<K> seenKeys = Sets.<K>newHashSetWithExpectedSize(keySet().size());
    @CheckForNull Node<K, V> next = head;
    @CheckForNull Node<K, V> current;

    }

    @Override
    public boolean isEmpty() {
      return !Iterables.any(unfiltered, predicate);
    }

    @Override
    public Iterator<E> iterator() {
      return Iterators.filter(unfiltered.iterator(), predicate);
    }

    @Override
    public Spliterator<E> spliterator() {
      return CollectSpliterators.filter(unfiltered.spliterator(), predicate);
    }

  }

  /**
   * A sensible default implementation of {@link #iterator}, in terms of {@link #listIterator()}. If
   * you override {@link #listIterator()}, you may wish to override {@link #iterator} to forward to
   * this implementation.
   *
   * @since 7.0
   */
  protected Iterator<E> standardIterator() {
    return listIterator();
  }

  /**

    return delegate.higher(checkValid(e));
  }

  @Override
  public boolean isEmpty() {
    return delegate.isEmpty();
  }

  @Override
  public Iterator<E> iterator() {
    return delegate.iterator();
  }

  @Override
  public E last() {
    return delegate.last();
  }

  @Override
  public @Nullable E lower(E e) {
    return delegate.lower(checkValid(e));
  }

  @CollectionSize.Require(absent = ZERO)
  public void testPutAllSomePresentConcurrentWithEntrySetIteration() {
    try {
      Iterator<Entry<K, V>> iterator = getMap().entrySet().iterator();
      putAll(MinimalCollection.of(e3(), e0()));
      iterator.next();
      fail("Expected ConcurrentModificationException");
    } catch (ConcurrentModificationException expected) {
      // success
    }
  }

   *
   * <p>The {@code entrySet}'s iterator returns entries in ascending element order according to this
   * multiset's comparator.
   */
  @Override
  Set<Entry<E>> entrySet();

  /**
   * {@inheritDoc}
   *
   * <p>The iterator returns the elements in ascending order according to this multiset's
   * comparator.
   */
  @Override
  Iterator<E> iterator();

  /**

import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.io.Serializable;
import java.util.AbstractCollection;
import java.util.Collection;
import java.util.Iterator;
import java.util.Spliterator;
import java.util.function.Predicate;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * GWT emulated version of {@link ImmutableCollection}.
 *

  public SampleElements(E e0, E e1, E e2, E e3, E e4) {
    this.e0 = e0;
    this.e1 = e1;
    this.e2 = e2;
    this.e3 = e3;
    this.e4 = e4;
  }

  @Override
  public Iterator<E> iterator() {
    return asList().iterator();
  }

  public List<E> asList() {
    return Arrays.asList(e0(), e1(), e2(), e3(), e4());
  }

  public static class Strings extends SampleElements<String> {
    public Strings() {

  public SampleElements(E e0, E e1, E e2, E e3, E e4) {
    this.e0 = e0;
    this.e1 = e1;
    this.e2 = e2;
    this.e3 = e3;
    this.e4 = e4;
  }

  @Override
  public Iterator<E> iterator() {
    return asList().iterator();
  }

  public List<E> asList() {
    return Arrays.asList(e0(), e1(), e2(), e3(), e4());
  }

  public static class Strings extends SampleElements<String> {
    public Strings() {

  @CollectionSize.Require(absent = ZERO)
  public void testAddAllConcurrentWithIteration() {
    try {
      Iterator<E> iterator = collection.iterator();
      assertTrue(collection.addAll(MinimalCollection.of(e3(), e0())));
      iterator.next();
      fail("Expected ConcurrentModificationException");
    } catch (ConcurrentModificationException expected) {
      // success
    }
  }