@CollectionFeature.Require(absent = ALLOWS_NULL_VALUES)
  public void testAddAllAtIndex_nullUnsupported() {
    List<E> containsNull = singletonList(null);
    assertThrows(NullPointerException.class, () -> getList().addAll(0, containsNull));
    expectUnchanged();
    expectNullMissingWhenNullUnsupported(
        "Should not contain null after unsupported addAll(n, containsNull)");
  }

  }

  // I guess it's technically a bug that ThrowIfUncheckedKnownUnchecked fires here.
  @SuppressWarnings("ThrowIfUncheckedKnownUnchecked")
  public void testThrowIfUnchecked_null() {
    assertThrows(NullPointerException.class, () -> throwIfUnchecked(null));
  }

  @J2ktIncompatible
  @GwtIncompatible // propagateIfPossible
  // I guess it's technically a bug that ThrowIfUncheckedKnownUnchecked fires here.

    assertSame(canonical, pool.intern(canonical));
    assertSame(canonical, pool.intern(not));
  }

  public void testStrong_null() {
    Interner<String> pool = Interners.newStrongInterner();
    assertThrows(NullPointerException.class, () -> pool.intern(null));
  }

  public void testStrong_builder() {
    int concurrencyLevel = 42;
    Interner<Object> interner =

          .put(IndexOutOfBoundsException.class, e -> e instanceof IndexOutOfBoundsException)
          .put(NoSuchElementException.class, e -> e instanceof NoSuchElementException)
          .put(NullPointerException.class, e -> e instanceof NullPointerException)
          .put(NumberFormatException.class, e -> e instanceof NumberFormatException)
          .put(RuntimeException.class, e -> e instanceof RuntimeException)

  }

  public void testNewReader() throws IOException {
    File asciiFile = getTestFile("ascii.txt");
    assertThrows(NullPointerException.class, () -> Files.newReader(asciiFile, null));

    assertThrows(NullPointerException.class, () -> Files.newReader(null, UTF_8));

    BufferedReader r = Files.newReader(asciiFile, US_ASCII);
    try {
      assertEquals(ASCII, r.readLine());

  public void testRemove_nullQueriesNotSupported() {
    try {
      assertNull(
          "remove(null) should return null or throw NullPointerException", getMap().remove(null));
    } catch (NullPointerException tolerated) {
    }
    expectUnchanged();
  }

  @MapFeature.Require({SUPPORTS_REMOVE, ALLOWS_NULL_KEY_QUERIES})
  public void testRemove_nullSupportedMissing() {

          .put(IndexOutOfBoundsException.class, e -> e instanceof IndexOutOfBoundsException)
          .put(NoSuchElementException.class, e -> e instanceof NoSuchElementException)
          .put(NullPointerException.class, e -> e instanceof NullPointerException)
          .put(NumberFormatException.class, e -> e instanceof NumberFormatException)
          .put(RuntimeException.class, e -> e instanceof RuntimeException)

          .put(IndexOutOfBoundsException.class, e -> e instanceof IndexOutOfBoundsException)
          .put(NoSuchElementException.class, e -> e instanceof NoSuchElementException)
          .put(NullPointerException.class, e -> e instanceof NullPointerException)
          .put(NumberFormatException.class, e -> e instanceof NumberFormatException)
          .put(RuntimeException.class, e -> e instanceof RuntimeException)

   * input element is mapped to one cell in the returned table, with the rows, columns, and values
   * generated by applying the specified functions.
   *
   * <p>The returned {@code Collector} will throw a {@code NullPointerException} at collection time
   * if the row, column, or value functions return null on any input.
   *
   * @since 21.0
   */
  public static <T extends @Nullable Object, R, C, V>

  }

  public void testBuilder_withImmutableEntryAndNullContents() {
    Builder<String, Integer> builder = new Builder<>();
    assertThrows(
        NullPointerException.class, () -> builder.put(immutableEntry("one", (Integer) null)));
    assertThrows(NullPointerException.class, () -> builder.put(immutableEntry((String) null, 1)));
  }

  public void testBuilderWithExpectedKeysNegative() {
    assertThrows(