return null;
    }
  }

  /**
   * Delegates to {@link Map#containsKey}. Returns {@code false} on {@code ClassCastException} and
   * {@code NullPointerException}.
   */
  static boolean safeContainsKey(Map<?, ?> map, @CheckForNull Object key) {
    checkNotNull(map);
    try {
      return map.containsKey(key);
    } catch (ClassCastException | NullPointerException e) {
      return false;
    }

      return null;
    }
  }

  /**
   * Delegates to {@link Map#containsKey}. Returns {@code false} on {@code ClassCastException} and
   * {@code NullPointerException}.
   */
  static boolean safeContainsKey(Map<?, ?> map, @CheckForNull Object key) {
    checkNotNull(map);
    try {
      return map.containsKey(key);
    } catch (ClassCastException | NullPointerException e) {
      return false;
    }