Java中List根据map的某个key去重的代码

/**

  * 根据map中的某个key 去除list中重复的map

  * @author shijing

  * @param list

  * @param mapkey

  * @return

  */

public static list<map<string, object>> removerepeatmapbykey(list<map<string, object>>

     list, string mapkey){

   if (collectionutils.isnullorempty(list)) return null ;

    //把list中的数据转换成msp,去掉同一id值多余数据，保留查找到第一个id值对应的数据

   list<map<string, object>> listmap = new arraylist<>();

   map<string, map> msp = new hashmap<>();

   for ( int i = list.size()- 1 ; i>= 0 ; i--){

     map map = list.get(i);

     string id = (string)map.get(mapkey);

     map.remove(mapkey);

     msp.put(id, map);

   }

   //把msp再转换成list,就会得到根据某一字段去掉重复的数据的list<map>

   set<string> mspkey = msp.keyset();

   for (string key: mspkey){

     map newmap = msp.get(key);

     newmap.put(mapkey, key);

     listmap.add(newmap);

   }

   return listmap;

}

public static void main(string[] args) {

     map<string, map> msp = new hashmap<string, map>();

     list<map<string, object>> list = new arraylist<map<string, object>>();

     list<map<string, object>> listmap = new arraylist<map<string,object>>();

     map<string, object> map1 = new hashmap<string, object>();

     map1.put( "id" , "1123" );

     map1.put( "name" , "张三" );

     map<string, object> map2 = new hashmap<string, object>();

     map2.put( "id" , "2" );

     map2.put( "name" , "李四" );

     map<string, object> map3 = new hashmap<string, object>();

     map3.put( "id" , "1123" );

     map3.put( "name" , "王五" );

     map<string, object> map4 = new hashmap<string, object>();

     map4.put( "id" , "3" );

     map4.put( "name" , "赵六" );

     list.add(map1);

     list.add(map2);

     list.add(map3);

     list.add(map4);

     system.out.println( "初始数据：" + list.tostring());

     system.out.println( "去重之后：" + removerepeatmapbykey(list, "id" ));

   }