@Override
  public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + ((author == null) ? 0 : author.hashCode());
    result = prime * result + currentQuantity;
    result = prime * result + ((description == null) ? 0 : description.hashCode());
    result = prime * result + idNumber;
    result = prime * result + (int) (isbn ^ (isbn >>> 32));
    result = prime * result + ((publishYear == null) ? 0 : publishYear.hashCode());
    result = prime * result + ((publisher == null) ? 0 : publisher.hashCode());
    result = prime * result + ((searchGenre == null) ? 0 : searchGenre.hashCode());
    result = prime * result + ((title == null) ? 0 : title.hashCode());
    result = prime * result + totalQuantity;
    result = prime * result + ((typeName == null) ? 0 : typeName.hashCode());
    return result;
  }