給晟豪

Main.java

 class Main() {
  public static void main(String[] arge) {
          Notice notice1 = new Notice(4, "課堂規定", "老師", new Date());
          Notice notice2 = new Notice(8, "提交作業", "班代", new Date());
          Notice notice3 = new Notice(3, "考試詳情", "老師", new Date());

          ArrayList<Notice> noticeList = new ArrayList<>(); //加入泛型，讓ArrayList知道陣列裡面的物件類型
          noticeList.add(notice1);
          noticeList.add(notice2);
          noticeList.add(notice3);

          System.out.println("未排序公告內容：");
          for (Notice n:noticeList)
              System.out.println(n);

          Collections.sort(noticeList,
                  new Comparator<Notice>() {
                      public int compare(Notice n1, Notice n2) {
                         if (n1.getId() > n2.getId())
                             return 1;
                         else
                             return -1;
                      }
                  });

          System.out.println("排序後公告內容：");
          for (Notice n:noticeList)
              System.out.println(n);
      }
}

Notice.java

import java.util.Date;

class Notice {
    private int id;
    private String s1;
    private String s2;

    public Notice(int i, String s1, String s2, Date date) {
        this.id = i;
        this.s1 = s1;
        this.s2 = s2;
    }

    public int getId() {
        return id;
    }

    public String getTitle() {
        return s1;
    }

    @Override
    public String toString() {
        return "Notice{" +
                "id=" + id +
                ", s1='" + s1 + '\'' +
                ", s2='" + s2 + '\'' +
                '}';
    }
}