checkNotNull(entry.getValue());
        @SuppressWarnings("unchecked") // all supported methods are covariant
        Entry<K, V> immutableEntry = (Entry<K, V>) entry;
        entries.add(immutableEntry);
      } else {
        entries.add(entryOf((K) entry.getKey(), (V) entry.getValue()));
      }
      return this;
    }

    @CanIgnoreReturnValue
    public Builder<K, V> putAll(Map<? extends K, ? extends V> map) {

      return new FilteredCollection<>(unfiltered, Predicates.and(predicate, newPredicate));
    }

    @Override
    public boolean add(@ParametricNullness E element) {
      checkArgument(predicate.apply(element));
      return unfiltered.add(element);
    }

    @Override
    public boolean addAll(Collection<? extends E> collection) {
      for (E element : collection) {

 * {@code asMap} has a few subtleties. As long as the set of keys remains unchanged, adding or
 * removing mappings does not affect the key iteration order. However, if you remove all values
 * associated with a key and then add the key back to the multimap, that key will come last in the
 * key iteration order.
 *
 * <p>The multimap does not store duplicate key-value pairs. Adding a new key-value pair equal to an
 * existing key-value pair has no effect.

    Set<String> presentAsSet = Optional.of("a").asSet();
    try {
      presentAsSet.add("b");
      fail();
    } catch (UnsupportedOperationException expected) {
    }
  }

  public void testAsSet_absentIsImmutable() {
    Set<Object> absentAsSet = Optional.absent().asSet();
    try {
      absentAsSet.add("foo");
      fail();
    } catch (UnsupportedOperationException expected) {
    }
  }

          SpliteratorDecompositionStrategy.ALL_STRATEGIES) {
        List<E> resultsForStrategy = new ArrayList<>();
        strategy.forEach(spliteratorSupplier.get(), resultsForStrategy::add);

        // TODO(cpovirk): better failure messages
        if ((characteristics & Spliterator.NONNULL) != 0) {
          assertFalse(resultsForStrategy.contains(null));
        }

        .testEquals();
  }

  public void testEqualsFalse() {
    List<Entry<K, V>> targetEntries = new ArrayList<>(getSampleElements());
    targetEntries.add(Helpers.mapEntry(k0(), v3()));
    new EqualsTester()
        .addEqualityGroup(multimap())
        .addEqualityGroup(getSubjectGenerator().create(targetEntries.toArray()))
        .testEquals();
  }

    int expectedHashCode = 0;
    for (E element : elements) {
      expectedHashCode += ((element == null) ? 0 : element.hashCode());
    }

    elements.add(null);
    collection = getSubjectGenerator().create(elements.toArray());
    assertEquals(
        "A Set's hashCode() should be the sum of those of its elements (with "

    public BigInteger next(BigInteger value) {
      return value.add(BigInteger.ONE);
    }

    @Override
    public BigInteger previous(BigInteger value) {
      return value.subtract(BigInteger.ONE);
    }

    @Override
    BigInteger offset(BigInteger origin, long distance) {
      checkNonnegative(distance, "distance");
      return origin.add(BigInteger.valueOf(distance));
    }

    @Override

                    for (Object e : elements) {
                      Entry<?, ?> entry = (Entry<?, ?>) e;
                      checkNotNull(entry.getValue());
                      set.add((String) checkNotNull(entry.getKey()));
                    }
                    return Maps.asMap(
                        set,
                        new Function<String, Integer>() {

      // Create a copy of that, with the desired value for each value
      Collection<Entry<K, V>> entries = new ArrayList<>(elements.length);
      int i = 0;
      for (Entry<K, V> entry : originalEntries) {
        entries.add(Helpers.mapEntry(entry.getKey(), valuesArray[i++]));
      }

      return mapGenerator.create(entries.toArray()).values();
    }

    @Override
    public V[] createArray(int length) {
      V[] vs =