private HalfEdge insert(Coordinate orig,Coordinate dest,HalfEdge eAdj){
  HalfEdge e=create(orig,dest);
  if (eAdj != null) {
    eAdj.insert(e);
  }
 else {
    vertexMap.put(orig,e);
  }
  HalfEdge eAdjDest=(HalfEdge)vertexMap.get(dest);
  if (eAdjDest != null) {
    eAdjDest.insert(e.sym());
  }
 else {
    vertexMap.put(dest,e.sym());
  }
  return e;
}

private HalfEdge insert ( Coordinate orig , Coordinate dest , HalfEdge eAdj ) { HalfEdge e = create ( orig , dest ) ; if ( eAdj != null ) { eAdj . insert ( e ) ; } else { vertexMap . put ( orig , e ) ; } HalfEdge eAdjDest = ( HalfEdge ) vertexMap . get ( dest ) ; if ( eAdjDest != null ) { eAdjDest . insert ( e . sym ( ) ) ; } else { vertexMap . put ( dest , e . sym ( ) ) ; } return e ; }
inserts an edge not already present into the graph .
