public static String getName(int difficulty, int i) {
        if (instance == null) {
            return null;
        }
        switch (difficulty) {
            case Grid.DIFFICULTY_EASY: return instance.easyName[i];
            case Grid.DIFFICULTY_MEDIUM: return instance.mediumName[i];
            case Grid.DIFFICULTY_HARD: return instance.hardName[i];
            case Grid.DIFFICULTY_EXTREME: return instance.extremeName[i];
            default: return null;
        }
    }