public class RussianDoll {   // version 2

  private RussianDoll inner;

  public RussianDoll(RussianDoll rd) {
    inner = rd;
  }
  
  public RussianDoll smaller() throws NegativeException {
    if (this == null)   // what's wrong with this?
       throw NegativeException;
    return inner;
  }

  public RussianDoll bigger() {
    return new RussianDoll(this);
  }

  public static void main(String args[]) throws NegativeException {
    // neither of these works
    RussianDoll rd1 = null.bigger().bigger().bigger().smaller().bigger();
    RussianDoll rd2 = ((RussianDoll)null).bigger().bigger().bigger().smaller().bigger();
  }
}