/** * Adds vertex to DAG. If vertex of given label already exist in DAG no vertex is added * * @param label The label of the Vertex * @return New vertex if vertex of given label was not present in the DAG or existing vertex if vertex of given * label was already added to DAG */ public Vertex addVertex( final String label ) { Vertex retValue = null; // check if vertex is already in DAG if ( vertexMap.containsKey( label ) ) { retValue = vertexMap.get( label ); } else { retValue = new Vertex( label ); vertexMap.put( label, retValue ); vertexList.add( retValue ); } return retValue; }