@Override
    public boolean equals(Object obj) {
	if (this == obj)
	    return true;
	if (obj == null)
	    return false;
	if (getClass() != obj.getClass())
	    return false;
	Book other = (Book) obj;
	if (id == null) {
	    if (other.id != null)
		return false;
	} else if (!id.equals(other.id))
	    return false;
	if (tittle == null) {
	    if (other.tittle != null)
		return false;
	} else if (!tittle.equals(other.tittle))
	    return false;
	return true;
    }