public void add(Edge e){
  edges.add(e);
  OrientedCoordinateArray oca=new OrientedCoordinateArray(e.getCoordinates());
  ocaMap.put(oca,e);
}

public void add ( Edge e ) { edges . add ( e ) ; OrientedCoordinateArray oca = new OrientedCoordinateArray ( e . getCoordinates ( ) ) ; ocaMap . put ( oca , e ) ; }
insert an edge unless it is already in the list
