public void handleRequest(PlanetEnum request) {
    
      if(request == PlanetEnum.VENUS) {
      System.out.println("VenusHandler handles" + request) ;
      System.out.println("Venus is poisonous.\n") ;
      }
      else {
         System.out.println("VenusHandler doesn't handle" + request) ;
        if(successor != null) {
          successor.handleRequest(request) ;
               }  
           }
      }