_id1 = "UndirectedEdge [" + source.id() + "]<->[" + dest.id() + "]"; _id2 = "UndirectedEdge [" + dest.id() + "]<->[" + source.id() + "]";
	public UEdge(UVertex source, UVertex dest, double length) {		super("UndirectedEdge ["			+ source.id() + "]<->["			+ dest.id() + "]");		if(source == null || dest == null || source.equals(dest)) {			throw new java.lang.IllegalArgumentException("Could not create edge");		}		_v = new Pair(source, dest);		_len = length;	}