public static PlanetHandler setUpChain() {
   PlanetHandler mercuryHandler = new MercuryHandler();
   PlanetHandler venusHandler = new VenusHandler();
   PlanetHandler earthHandler = new EarthHandler();
   mercuryHandler.setSuccessor(venusHandler);
   venusHandler.setSuccessor(earthHandler);
   return mercuryHandler;
   }