public void addParentRelation(Relation relation){
  if (parentRelations == null) {
    parentRelations=new ArrayList<Relation>();
  }
  parentRelations.add(relation);
}

public void addParentRelation ( Relation relation ) { if ( parentRelations == null ) { parentRelations = new ArrayList < Relation > ( ) ; } parentRelations . add ( relation ) ; }
add reference to parent relation does not check id to avoid dups !
