Collections.sort对象排序失效问题

今天做一个对象集合排序，看着代码没啥问题，可排序就是不起作用，代码如下。

public static void main(String[] args) {
        List<student> list=new ArrayList<>();
        student o1=new student();
        o1.setTotalNum(10);
        o1.setEndNum(2);
        student o2=new student();
        o2.setTotalNum(8);
        o2.setEndNum(2);
        student o3=new student();
        o3.setTotalNum(100);
        o3.setEndNum(2);
        list.add(o2);
        list.add(o3);
        list.add(o1);
        Collections.sort(list, new Comparator<student>() {
            @Override
            public int compare(student o1, student o2) {
                return  o2.getTotalNum()-o1.getTotalNum();
            }
        });

        System.out.println(list);

    }

输出如下，没有进行排序。

[QuarantineInfoController.student(totalNum=100, endNum=2), QuarantineInfoController.student(totalNum=10, endNum=2), QuarantineInfoController.student(totalNum=8, endNum=2)]

最终找到原因， 

List<student> list=new ArrayList<>();要改为List<student> list=new ArrayList<student>();

正确代码如下

 public static void main(String[] args) {
        List<student> list=new ArrayList<student>();
        student o1=new student();
        o1.setTotalNum(10);
        o1.setEndNum(2);
        student o2=new student();
        o2.setTotalNum(8);
        o2.setEndNum(2);
        student o3=new student();
        o3.setTotalNum(100);
        o3.setEndNum(2);
        list.add(o2);
        list.add(o3);
        list.add(o1);
        Collections.sort(list, new Comparator<student>() {
            @Override
            public int compare(student o1, student o2) {
                return  o2.getTotalNum()-o1.getTotalNum();
            }
        });

输出：

[QuarantineInfoController.student(totalNum=100, endNum=2), QuarantineInfoController.student(totalNum=10, endNum=2), QuarantineInfoController.student(totalNum=8, endNum=2)]

这样就排序了，小小的细节，大大的问题呀！

标签：sort,list,Collections,student,new,排序,o3,o2,o1
来源： https://blog.csdn.net/letterss/article/details/121094258