checkState(count() > 1);
    return sumOfProductsOfDeltas / (count() - 1);
  }

  /**
   * Returns the <a href="http://mathworld.wolfram.com/CorrelationCoefficient.html">Pearson's or
   * product-moment correlation coefficient</a> of the values. The count must greater than one, and
   * the {@code x} and {@code y} values must both have non-zero population variance (i.e. {@code

  }

  private static void assertEvalsToTrue(Predicate<? super @Nullable Integer> predicate) {
    assertTrue(predicate.apply(0));
    assertTrue(predicate.apply(1));
    assertTrue(predicate.apply(null));
  }

  private static void assertEvalsToFalse(Predicate<? super @Nullable Integer> predicate) {
    assertFalse(predicate.apply(0));
    assertFalse(predicate.apply(1));
    assertFalse(predicate.apply(null));
  }

    <T extends @Nullable Object> Predicate<T> withNarrowedType() {
      return (Predicate<T>) this;
    }
  }

  /** @see Predicates#not(Predicate) */
  private static class NotPredicate<T extends @Nullable Object>
      implements Predicate<T>, Serializable {
    final Predicate<T> predicate;

    NotPredicate(Predicate<T> predicate) {
      this.predicate = checkNotNull(predicate);
    }

    }
  }

  static final Predicate<String> FILTER_KEYS =
      new Predicate<String>() {
        @Override
        public boolean apply(@Nullable String string) {
          return !"banana".equals(string) && !"eggplant".equals(string);
        }
      };

  static final Predicate<String> FILTER_VALUES =
      new Predicate<String>() {
        @Override

   * {@code predicate}.
   *
   * @since 2.0
   */
  public static <T extends @Nullable Object> int indexOf(
      Iterator<T> iterator, Predicate<? super T> predicate) {
    checkNotNull(predicate, "predicate");
    for (int i = 0; iterator.hasNext(); i++) {
      T current = iterator.next();
      if (predicate.apply(current)) {
        return i;
      }
    }

import com.google.common.base.Predicate;
import java.util.Collection;
import java.util.Map;
import java.util.Map.Entry;

/**
 * Tests for Multimaps.filterEntries().asMap().
 *
 * @author Jared Levy
 */
@GwtIncompatible(value = "untested")
public class MultimapsFilterEntriesAsMapTest extends AbstractMultimapAsMapImplementsMapTest {
  private static final Predicate<Entry<String, Integer>> PREDICATE =

    extends FilteredEntryMultimap<K, V> implements FilteredSetMultimap<K, V> {

  FilteredEntrySetMultimap(SetMultimap<K, V> unfiltered, Predicate<? super Entry<K, V>> predicate) {
    super(unfiltered, predicate);
  }

  @Override
  public SetMultimap<K, V> unfiltered() {
    return (SetMultimap<K, V>) unfiltered;
  }

  @Override
  public Set<V> get(@ParametricNullness K key) {

    FluentIterable<String> iterable = FluentIterable.<String>from(list);
    Predicate<String> predicate = Predicates.equalTo("pants");

    assertFalse(iterable.anyMatch(predicate));
    list.add("cool");
    assertFalse(iterable.anyMatch(predicate));
    list.add("pants");
    assertTrue(iterable.anyMatch(predicate));
  }

  public void testAllMatch() {
    List<String> list = Lists.newArrayList();

   *
   * <p><b>{@code Stream} equivalent:</b> {@link Stream#anyMatch} (same).
   */
  public final boolean anyMatch(Predicate<? super E> predicate) {
    return Iterables.any(getDelegate(), predicate);
  }

  /**
   * Returns {@code true} if every element in this fluent iterable satisfies the predicate. If this

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Predicate;
import java.util.Map.Entry;
import java.util.Set;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Implementation of {@link Multimaps#filterKeys(SetMultimap, Predicate)}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault