對MapString Object集合進行排序

        Collections.sort(list_a, new Comparator<Map<String,Object>>() {  
            @Override  
            public int compare(Map<String,Object> firstMapEntry,   
                       Map<String,Object> secondMapEntry) {  
                    
                  int  tag1=(Integer) firstMapEntry.get("tag");  
                    
                  int  tag2=(Integer) secondMapEntry.get("tag");  
              return  (tag1>tag2?1:-1);  
            }  
          });