@Override
  public String toString() {
    int size = getSize();
    StringBuilder sb = new StringBuilder();
    sb.append("Vector ").append(size).append(" { ");
    for (int i = 0; i < size; i++) {
      if (i != 0) sb.append(", ");
      sb.append(get(i));
    }
    return sb.append(" }").toString();
  }
@Override
  public String toString()