@SuppressWarnings("unchecked") // Empty array is safe to cast.
  private static <K, V> HamtPMap<K, V>[] emptyChildren() {
    return (HamtPMap<K, V>[]) EMPTY_CHILDREN;
  }
@ SuppressWarnings ( "unchecked" ) private static < K , V > HamtPMap < K , V > [ ] emptyChildren ( ) { return ( HamtPMap < K , V > [ ] ) EMPTY_CHILDREN ; }
Returns an empty array of child maps.