throws an error if a vertex is attempted to be removed concode_field_sep int numNodes concode_elem_sep Iterator<Vertex> it concode_elem_sep List<Vertex> verts concode_field_sep Vertex next concode_elem_sep Iterator<Vertex> iterator concode_elem_sep Graph readGraph concode_elem_sep boolean hasNext concode_elem_sep void addEdge concode_elem_sep void addDirectedEdge
void function ( ) { throw new UnsupportedOperationException ( ) ; }