* performance for unescaped strings (as measured by {@code CharEscapersBenchmark}).
   *
   * @param string the literal string to be escaped
   * @return the escaped form of {@code string}
   * @throws NullPointerException if {@code string} is null
   * @throws IllegalArgumentException if invalid surrogate characters are encountered
   */
  @Override
  public String escape(String string) {
    checkNotNull(string);

    assertThrows(
        NullPointerException.class,
        () -> Maps.toMap((Iterable<String>) strings, Functions.constant("foo")));
  }

  public void testToMapWithNullValues() {
    Iterable<String> strings = ImmutableList.of("one", "two", "three");
    assertThrows(NullPointerException.class, () -> Maps.toMap(strings, Functions.constant(null)));
  }

   *
   * <p><b>Java 8+ users:</b> use {@link Integer#parseUnsignedInt(String)} instead.
   *
   * @throws NumberFormatException if the string does not contain a valid unsigned {@code int} value
   * @throws NullPointerException if {@code s} is null (in contrast to {@link
   *     Integer#parseInt(String)})
   */
  @CanIgnoreReturnValue
  public static int parseUnsignedInt(String s) {
    return parseUnsignedInt(s, 10);
  }

   * Delegates to {@link Map#get}. Returns {@code null} on {@code ClassCastException} and {@code
   * NullPointerException}.
   */
  static <V extends @Nullable Object> @Nullable V safeGet(Map<?, V> map, @Nullable Object key) {
    checkNotNull(map);
    try {
      return map.get(key);
    } catch (ClassCastException | NullPointerException e) {
      return null;
    }
  }

  /**

   * Delegates to {@link Map#get}. Returns {@code null} on {@code ClassCastException} and {@code
   * NullPointerException}.
   */
  static <V extends @Nullable Object> @Nullable V safeGet(Map<?, V> map, @Nullable Object key) {
    checkNotNull(map);
    try {
      return map.get(key);
    } catch (ClassCastException | NullPointerException e) {
      return null;
    }
  }

  /**

    assertEquals(0, getMultiset().remove(null, 2));
  }

  @CollectionFeature.Require(value = SUPPORTS_REMOVE, absent = ALLOWS_NULL_QUERIES)
  public void testRemove_nullForbidden() {
    assertThrows(NullPointerException.class, () -> getMultiset().remove(null, 2));
  }

  @CollectionSize.Require(SEVERAL)
  @CollectionFeature.Require(SUPPORTS_REMOVE)
  public void testRemoveAllIgnoresCount() {
    initThreeCopies();

    assertEquals(0, getMultiset().remove(null, 2));
  }

  @CollectionFeature.Require(value = SUPPORTS_REMOVE, absent = ALLOWS_NULL_QUERIES)
  public void testRemove_nullForbidden() {
    assertThrows(NullPointerException.class, () -> getMultiset().remove(null, 2));
  }

  @CollectionSize.Require(SEVERAL)
  @CollectionFeature.Require(SUPPORTS_REMOVE)
  public void testRemoveAllIgnoresCount() {
    initThreeCopies();

    assertEquals(size + 1, multimap().size());
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_VALUES)
  public void testPutNullValue_unsupported() {
    assertThrows(NullPointerException.class, () -> multimap().put(k1(), null));

    expectUnchanged();
  }

  @MapFeature.Require({SUPPORTS_PUT, ALLOWS_NULL_KEYS})
  public void testPutNullKey() {
    int size = getNumElements();

    testComparator(comparator, Integer.MIN_VALUE, -1, 0, 1, Integer.MAX_VALUE);
    assertThrows(NullPointerException.class, () -> comparator.compare(1, null));
    assertThrows(NullPointerException.class, () -> comparator.compare(null, 2));
    assertThrows(NullPointerException.class, () -> comparator.compare(null, null));
    assertSame(comparator, reserialize(comparator));

    testComparator(comparator, Integer.MIN_VALUE, -1, 0, 1, Integer.MAX_VALUE);
    assertThrows(NullPointerException.class, () -> comparator.compare(1, null));
    assertThrows(NullPointerException.class, () -> comparator.compare(null, 2));
    assertThrows(NullPointerException.class, () -> comparator.compare(null, null));
    assertSame(comparator, reserialize(comparator));