multimap.put("bar", 5);
    multimap.put("bar", -1);
    multimap.put(nullKey, nullValue);
    multimap.put("foo", nullValue);
    multimap.put(nullKey, 5);
    multimap.put("foo", 2);

    if (permitsDuplicates) {
      assertEquals(9, multimap.size());
    } else {
      assertEquals(8, multimap.size());
    }

    Multimap<@Nullable String, @Nullable Integer> unmodifiable;

  static void populateMultimapForGet(Multimap<Integer, String> multimap, String[] elements) {
    multimap.put(2, "foo");
    for (String element : elements) {
      multimap.put(3, element);
    }
  }

  static void populateMultimapForKeySet(Multimap<String, Integer> multimap, String[] elements) {
    for (String element : elements) {
      multimap.put(element, 2);
      multimap.put(element, 3);
    }
  }

    } catch (UnsupportedOperationException expected) {
    }
    assertMultimapRemainsUnmodified(multimap, originalEntries);

    // Test #putAll(Multimap<K, V>)
    Multimap<K, V> multimap2 = ArrayListMultimap.create();
    multimap2.put(sampleKey, sampleValue);
    try {
      multimap.putAll(multimap2);
      fail("putAll(Multimap<K, V>) succeeded on unmodifiable multimap");

   *
   * @throws NullPointerException if any key or value in {@code multimap} is null
   */
  public static <K, V> ImmutableMultimap<K, V> copyOf(Multimap<? extends K, ? extends V> multimap) {
    if (multimap instanceof ImmutableMultimap) {
      @SuppressWarnings("unchecked") // safe since multimap is not writable
      ImmutableMultimap<K, V> kvMultimap = (ImmutableMultimap<K, V>) multimap;
      if (!kvMultimap.isPartialView()) {

    Multimap<String, Integer> multimap = ImmutableSetMultimap.of();
    assertFalse(multimap.containsKey("foo"));
    assertFalse(multimap.containsValue(1));
    assertFalse(multimap.containsEntry("foo", 1));
    assertTrue(multimap.entries().isEmpty());
    assertTrue(multimap.equals(HashMultimap.create()));
    assertEquals(emptySet(), multimap.get("foo"));
    assertEquals(0, multimap.hashCode());
    assertTrue(multimap.isEmpty());

    multimap.put("foo", -1);
    multimap.put(null, null);
    multimap.put("bar", 1);
    multimap.put("foo", 2);
    multimap.put(null, 0);
    multimap.put("bar", 2);
    multimap.put("bar", null);
    multimap.put("foo", null);
    multimap.put("foo", 4);
    multimap.put(null, -1);
    multimap.put("bar", 3);
    multimap.put("bar", 1);
    multimap.put("foo", 1);

    assertEquals(

  static void populateMultimapForGet(Multimap<Integer, String> multimap, String[] elements) {
    multimap.put(2, "foo");
    for (String element : elements) {
      multimap.put(3, element);
    }
  }

  static void populateMultimapForKeySet(Multimap<String, Integer> multimap, String[] elements) {
    for (String element : elements) {
      multimap.put(element, 2);
      multimap.put(element, 3);
    }
  }

    multimap.put("foo", -1);
    multimap.put(null, null);
    multimap.put("bar", 1);
    multimap.put("foo", 2);
    multimap.put(null, 0);
    multimap.put("bar", 2);
    multimap.put("bar", null);
    multimap.put("foo", null);
    multimap.put("foo", 4);
    multimap.put(null, -1);
    multimap.put("bar", 3);
    multimap.put("bar", 1);
    multimap.put("foo", 1);

    assertEquals(

    } catch (UnsupportedOperationException expected) {
    }
    assertMultimapRemainsUnmodified(multimap, originalEntries);

    // Test #putAll(Multimap<K, V>)
    Multimap<K, V> multimap2 = ArrayListMultimap.create();
    multimap2.put(sampleKey, sampleValue);
    try {
      multimap.putAll(multimap2);
      fail("putAll(Multimap<K, V>) succeeded on unmodifiable multimap");

   */
  public <K extends K0, V extends V0> Multimap<K, V> build(
      Multimap<? extends K, ? extends V> multimap) {
    Multimap<K, V> result = build();
    result.putAll(multimap);
    return result;
  }

  /**
   * A specialization of {@link MultimapBuilder} that generates {@link ListMultimap} instances.
   *
   * @since 16.0
   */
  public abstract static class ListMultimapBuilder<