class Stamp implements Serializable {

    @Override
    public boolean equals(Object o) {
        if (!(o instanceof Stamp)) {
            return false;
        }
        else {
            Stamp other = (Stamp) o;
            return id.equals(other.getId()) && event.equals(other.getEvent());
        }
    }

    public  Stamp();
      Stamp(ID id, Event event);

}