List<T> 根据某个字段排序

List list = new ArrayList();                 //......                          Collections.sort(list, new MyComparator());                 class MyComparator implements Comparator        {            //这里的1hs和rhs就是list里任意的两个对象，然后按需求把这个方法填完整就行了           public int compare(Person lhs, Person rhs)     {    if (lhs.num > rhs.num)   {return 1;   }   if (lhs.num == rhs.num)  {return 0;  }  if (lhs.num < rhs.num) {return -1; } return 0;      }        }