根据Map中值的对象的属性排序

1. 首先public class BaseVisitor implements omparable<BaseVisitor>
2. public int compareTo(BaseVisitor o) {
//从大到小
return o.getVisitNum() - this.getVisitNum();
}
3.循环编译Map，把对象存到list里，然后执行Collections.sort(ltInfo);
   就可以了，如下：
List ltInfo = new ArrayList();
Set<Map.Entry<String, Object>> infos = mpDetailInfo.entrySet();
for (Map.Entry<String, Object> info : infos) {
ltInfo.add(info.getValue());
}
Collections.sort(ltInfo);