Method orNaturalOrder

output/java_guava/1.4.19/Maps.java:725–731

Returns the specified comparator if not null; otherwise returns Ordering.natural(). This method is an abomination of generics; the only purpose of this method is to contain the ugly type-casting in one place.

(@Nullable Comparator<? super E> comparator)

   */

  @SuppressWarnings("unchecked")
  static <E> Comparator<? super E> orNaturalOrder(@Nullable Comparator<? super E> comparator) {
    if (comparator != null) { // can't use ? : because of javac bug 5080917
      return comparator;
    }
    return (Comparator<E>) Ordering.natural();
  }

  /**
   * Returns a live {@link Map} view whose keys are the contents of {@code set}