@Override
  public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append("Matrix ").append(height).append("x").append(width).append(" { ");
    for (int i = 0, h = 0; h < height; h++) {
      if (h != 0) sb.append(", ");
      sb.append("{");
      for (int w = 0; w < width; w++, i++) {
        if (w != 0) sb.append(", ");
        sb.append(vector.get(i));
      }
      sb.append("}");
    }
    return sb.append(" }").toString();
  }
@Override
  public String toString()