* we're copying into a `contents` array whose type allows it to contain nulls. Still, it's
       * worth noting that we promise not to put nulls into the array in the first `size` elements.
       * We uphold that promise here because our callers promise that `elements` will not contain
       * nulls in its first `n` elements.
       */
      System.arraycopy(elements, 0, contents, size, n);
      size += n;

   */
  /*
   * By declaring <T> instead of <T extends @Nullable Object>, we declare this method as requiring a
   * stream whose elements are non-null. However, the method goes out of its way to still handle
   * nulls in the stream. This means that the method can safely be used with a stream that contains
   * nulls as long as the *last* element is *not* null.
   *

    static FactoryMethodReturnsNullButNotAnnotated returnsNull() {
      return null;
    }
  }

  static class FactoryMethodReturnsNullAndAnnotated {
    private FactoryMethodReturnsNullAndAnnotated() {}

    public static @Nullable FactoryMethodReturnsNullAndAnnotated returnsNull() {
      return null;
    }
  }

  static class FactoryMethodAcceptsNull {

        prepareUnmodifiableTests(HashMultimap.<String, Integer>create(), false, null, null);
    SerializableTester.reserializeAndAssert(unmodifiable);
  }

  @GwtIncompatible // slow (~10s)
  public void testUnmodifiableTreeMultimap() {
    checkUnmodifiableMultimap(TreeMultimap.<String, Integer>create(), false, "null", 42);
  }

  @J2ktIncompatible
  @GwtIncompatible // SerializableTester

    // [[null, null], [null], [1, null, 2], [1, 1], [1, 2], [1], [2], [], null]
    assertThat(sorted)
        .containsExactly(
            Lists.<@Nullable Integer>newArrayList(nullInt, nullInt),
            Lists.<@Nullable Integer>newArrayList(nullInt),
            Lists.<@Nullable Integer>newArrayList(1, null, 2),
            Lists.newArrayList(1, 1),
            Lists.newArrayList(1, 2),

    // [[null, null], [null], [1, null, 2], [1, 1], [1, 2], [1], [2], [], null]
    assertThat(sorted)
        .containsExactly(
            Lists.<@Nullable Integer>newArrayList(nullInt, nullInt),
            Lists.<@Nullable Integer>newArrayList(nullInt),
            Lists.<@Nullable Integer>newArrayList(1, null, 2),
            Lists.newArrayList(1, 1),
            Lists.newArrayList(1, 2),

    List<@Nullable String> list = newArrayList("a", null, "b", null, "a", null);
    assertEquals(2, frequency(list.iterator(), "a"));
    assertEquals(1, frequency(list.iterator(), "b"));
    assertEquals(0, frequency(list.iterator(), "c"));
    assertEquals(0, frequency(list.iterator(), 4.2));
    assertEquals(3, frequency(list.iterator(), null));
  }

  @GwtIncompatible // slow (~4s)

   * removal operations, and these are reflected in the underlying map.
   *
   * <p>It's acceptable for the underlying map to contain null keys, and even null values provided
   * that the function is capable of accepting null input. The transformed map might contain null
   * values, if the function sometimes gives a null result.
   *
   * <p>The returned map is not thread-safe or serializable, even if the underlying map is.
   *

    protected final ColumnInfo _columnDepth = cci("depth", "depth", null, null, Integer.class, "depth", null, false, false, false,
            "Integer", 0, 0, null, null, false, null, null, null, null, null, false);
    protected final ColumnInfo _columnDescription = cci("description", "description", null, null, String.class, "description", null, false,

    protected final ColumnInfo _columnUpdatedTime = cci("updatedTime", "updatedTime", null, null, Long.class, "updatedTime", null, false,
            false, false, "Long", 0, 0, null, null, false, null, null, null, null, null, false);
    protected final ColumnInfo _columnUrls = cci("urls", "urls", null, null, String.class, "urls", null, false, false, false, "keyword", 0,