➍

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((orderId == null) ? 0 : orderId.hashCode());
        return result;
    }

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

}