找出构造函数层次里的 bug

public class Main {
    static class Report {
        Report() {
            System.out.println(title());
        }

        String title() { return "report"; }
    }

    static final class MonthlyReport extends Report {
        private String month = "September";

        @Override
        String title() { return month.toUpperCase(); }
    }

    public static void main(String[] args) {
        new MonthlyReport();
    }
}