根据list里面对象的某个特定属性排序，若属性值为空的处理

Collections.sort(fileRecordDOList, Comparator.comparing(FileRecordDO::getOperateTime).reversed());

reversed()逆序排序,从大到小

若排序的属性值有空值，以上方法会报错，需要使用以下方法
升序：从小到大排序

1  
2 Collections.sort(userList, new Comparator<User>() {
3     @Override
4     public int compare(User o1, User o2) {
5         //若有空值可以在这里赋值
6         return o1.getName().compareTo(o2.getName());
7     }
8 });

降序：从大到小排序

1 Collections.sort(userList, new Comparator<User>() {
2     @Override
3     public int compare(User o1, User o2) {
4         //若有空值可以在这里赋值
5         return o2.getName().compareTo(o1.getName());
6     }
7 });

多条件排序

 1             Collections.sort(recentModifyPredictLogDTOList, new Comparator<RecentModifyPredictLogDTO>() {
 2                 @Override
 3                 public int compare(RecentModifyPredictLogDTO o1, RecentModifyPredictLogDTO o2) {
 4                     if (o2.getPredictUpdateCount().compareTo(o1.getPredictUpdateCount()) == 1) {
 5                         return 1;
 6                     } else if (o2.getPredictUpdateCount().compareTo(o1.getPredictUpdateCount()) == -1) {
 7                         return -1;
 8                     } else if (o2.getPredictUpdateCount().compareTo(o1.getPredictUpdateCount()) == 0) {
 9                         // 如果成交套数相等的话就按照响应速度升序
10                         if (o2.getPredictRealName().compareTo(o1.getPredictRealName()) == -1) {
11                             return 1;
12                         } else if (o2.getPredictRealName().compareTo(o1.getPredictRealName()) == 1) {
13                             return -1;
14                         } else if (o2.getPredictRealName().compareTo(o1.getPredictRealName()) == 0) {
15                             if (o2.getStockShortName().compareTo(o1.getStockShortName()) == -1) {
16                                 return 1;
17                             } else if (o2.getStockShortName().compareTo(o1.getStockShortName()) == 1) {
18                                 return -1;
19                             } else if (o2.getStockShortName().compareTo(o1.getStockShortName()) == 0) {
20                                 return 0;
21                             }
22                         }
23                     }
24                     return 0;
25                 }
26             });