code: @Override
    @Beta
    protected boolean standardContains(@NullableDecl Object object) {
      try {
        // any ClassCastExceptions are caught
        @SuppressWarnings("unchecked")
        SortedSet<Object> self = (SortedSet<Object>) this;
        Object ceiling = self.tailSet(object).first();
        return unsafeCompare(ceiling, object) == 0;
      } catch (ClassCastException | NoSuchElementException | NullPointerException e) {
        return false;
      }
    }
docs: A sensible definition of {@link #contains} in terms of the {@code first()} method of {@link
  #tailSet}. If you override {@link #tailSet}, you may wish to override {@link #contains} to
  forward to this implementation.
  
  @since 7.0