public String toString() {
		String s = "";

		final Iterator iter = nodes.values().iterator();

		while (iter.hasNext()) {
			final GraphNode node = (GraphNode) iter.next();
			s += "[" + node;
			s += " succs = " + node.succs();
			s += " preds = " + node.preds();
			s += "]\n";
		}

		return s;
	}