public boolean addChildPlanet(DimensionProperties child){
  if (child == this)   return false;
  childPlanets.add(child.getId());
  child.setParentPlanet(this);
  return true;
}

public boolean addChildPlanet ( DimensionProperties child ) { if ( child == this ) return false ; childPlanets . add ( child . getId ( ) ) ; child . setParentPlanet ( this ) ; return true ; }
does not check for hierarchy loops !
