public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		final Edge other = (Edge) obj;
		if (from == null) {
			if (other.from != null)
				return false;
		} else if (!from.equals(other.from))
			return false;
		if (to == null) {
			if (other.to != null)
				return false;
		} else if (!to.equals(other.to))
			return false;
		//if (w != other.w)
		//	return false;  dont't need to compare the weight, since the path only have unique weight
		return true;
	}