@SuppressWarnings("unchecked")
  public static <E extends OrdinalValue<E>> ImmutableOrdinalSet<E> of() {
    // safe unchecked: will contain no elements
    return (ImmutableOrdinalSet<E>) EMPTY_SET;
  }
@SuppressWarnings("unchecked")
  public static <E extends OrdinalValue<E>> ImmutableOrdinalSet<E> of() {
    
    return (ImmutableOrdinalSet<E>) EMPTY_SET;
  }
@ SuppressWarnings ( "unchecked" ) public static < E extends OrdinalValue < E > > ImmutableOrdinalSet < E > of ( ) { // safe unchecked: will contain no elements return ( ImmutableOrdinalSet < E > ) EMPTY_SET ; }
Returns singleton empty immutable ordinal set
@param <E> element type
@return empty set
Returns singleton empty immutable ordinal set