А тут можно через switch case реализовать?

public static void readKeyFromConsoleAndInitPlanet() throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String s = reader.readLine();
        if (s.equals(Planet.EARTH)) {
            thePlanet = Earth.getInstance();
        } else if (s.equals(Planet.MOON)) {
            thePlanet = Moon.getInstance();
        } else if (s.equals(Planet.SUN)) {
            thePlanet = Sun.getInstance();
        } else thePlanet = null;