对list中的对象进行排序

//降序
Collections.sort(listFollowBuddy,new Comparator<Buddy.FollowBuddy>(){ 
            @Override 
            public int compare(Buddy.FollowBuddy b1, Buddy.FollowBuddy b2) {
            int r=0;
            if(b1.getRecmdLevel()!=null&&b2.getRecmdLevel()!=null){
            r=b1.getRecmdLevel().compareTo(b2.getRecmdLevel());
            r=-r;//降序
            }else if(b1.getRecmdLevel()==null&&b2.getRecmdLevel()!=null){
            r=1;
            }else if(b1.getRecmdLevel()!=null&&b2.getRecmdLevel()==null){
            r=-1;
            }
            return r;
            } 
        });


//升序
Collections.sort(visitTimeModelListUp,new Comparator<VisitTimeModel>(){ 
            @Override 
            public int compare(VisitTimeModel b1, VisitTimeModel b2) {
            int r=0;
            if(b1.getTime()!=null&&b2.getTime()!=null){
            r=b1.getTime().compareTo(b2.getTime());
            }else if(b1.getTime()==null&&b2.getTime()!=null){
            r=1;
            }else if(b1.getTime()!=null&&b2.getTime()==null){
            r=-1;
            }
            return r;
            } 
        });