public void addEdge(String v, String w) {

		if (symbolTable.get(v) == null)
			addVertex(v);
		if (symbolTable.get(w) == null)
			addVertex(w);
		AdjacencyList vlist = (AdjacencyList) symbolTable.get(v);
		AdjacencyList wlist = (AdjacencyList) symbolTable.get(w);
		vlist.insert(w);
		wlist.insert(v);
	}