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