@Override
    public boolean equals(Object obj) {
	if (this == obj)
	    return true;
	if (obj == null)
	    return false;
	if (getClass() != obj.getClass())
	    return false;
	AbstractAvaObject other = (AbstractAvaObject) obj;
	if (id != other.id)
	    return false;
	if (position == null) {
	    if (other.position != null)
		return false;
	} else if (!position.equals(other.position))
	    return false;
	if (Double.doubleToLongBits(size) != Double.doubleToLongBits(other.size))
	    return false;
	return true;
    }