switch (backOffLevel) { case 0: return history.get(0, 0) == topSym; case 1: return history.get(0, 0) == topSym; case 2: return false; } return false;
return history.get(0, 0) == topSym;
  public boolean removeHistory(int backOffLevel, Event history) {    // this method assumes the parent component of histories for    // back-off levels 0 and 1 will be at index 0.  IF THIS CHANGES,    // this method will need to change accordingly.    switch (backOffLevel) {    case 0:      return history.get(0, 0) == topSym;    case 1:      return history.get(0, 0) == topSym;    case 2:      return false;    }    return false;  }