public static <Vertex> DiGraph<Vertex> diGraph
	(final Collection<Vertex> roots, final ForwardNavigator<Vertex> fnavigator) {
	return new DiGraph<Vertex>() {
	    public Collection<Vertex> getRoots() { return roots; }
	    public ForwardNavigator<Vertex> getForwardNavigator() { 
		return fnavigator;
	    }
	};
    }
public static < Vertex > DiGraph < Vertex > diGraph ( final Collection < Vertex > roots , final ForwardNavigator < Vertex > fnavigator ) { return new DiGraph < Vertex > ( ) { public Collection < Vertex > getRoots ( ) { return roots ; } public ForwardNavigator < Vertex > getForwardNavigator ( ) { return fnavigator ; } } ; }
Constructs a <code>DiGraph</code> object.

@param roots Collection of root vertices.  This collection
will be used directly, without being cloned or copied into
another collection; none of the graph algorithms will mutate
it.

@param fnavigator forward digraph navigator