public static void main(String[] args) {
        // ɼù
        SchoolReport sr;
        sr = new FouthGradeSchoolReport(); // ԭװĳɼ
        // ߷˵ĳɼ
        sr = new HighScoreDecorator(sr);
        // ּ˳ɼ˵
        sr = new SortDecorator(sr);
        // ɼ
        sr.report();
        // Ȼϰ֣һܿģǩ
        sr.sign(""); // ҽСϰֵȻ
    }