sclass ImmutableSortedSet<A> extends AbstractSet<A> {
  O[] array;
  
  *() { array = emptyObjectArray(); }
  *(Collection<? extends A> elements) {
    array = toObjectArray(elements);
  }
  
  public Iterator<S> iterator() { ret arrayIterator(array); }
  public int size() { ret l(array); }
  public bool contains(O o) {
    ret Arrays.binarySearch(array, o) >= 0;
  }
}