下面java编程中如何实现？

package test;

public class Test2 {
/**
* 把字符串：
* [{"username":"小明","userid":"USER2015082500005","ssbm":"行政部"},
* {"username":"小红","userid":"USER2015082500024","ssbm":"行政部"},
* {"username":"小东","userid":"USER2015082500027","ssbm":"市场开发部"},
* {"username":"小兰","userid":"USER2015082500040","ssbm":"安全运营部"}]
* 转换为：
* {"行政部":[{"username":"小明","userid":"USER2015082500005","ssbm":"行政部"},
* {"username":"小红","userid":"USER2015082500024","ssbm":"行政部"}],
* "财务部":[{"username":"小东","userid":"USER2015082500027","ssbm":"市场开发部"}],
* "安全运营部":[{"username":"小兰","userid":"USER2015082500040","ssbm":"安全运营部"}]}
* @param args
/
public static void main(String[] args) {
/----------------完善代码 begin----------------*/

    /*----------------完善代码  end----------------*/
}

}

最笨的方法
public static void main(String[] args) {
List> list = new ArrayList<>();
Map map1 = new HashMap();
map1.put("username","小明");
map1.put("userid","USER2015082500005" );
map1.put("ssbm","行政部" );

    Map<String,Object> map2 = new HashMap<String, Object>();
    map2.put("username","小红");
    map2.put("userid","USER2015082500005" );
    map2.put("ssbm","行政部" );
    Map<String,Object> map3 = new HashMap<String, Object>();
    map3.put("username","小懂");
    map3.put("userid","USER2015082500005" );
    map3.put("ssbm","市场开发部" );
    Map<String,Object> map4 = new HashMap<String, Object>();
    map4.put("username","小蓝");
    map4.put("userid","USER2015082500005" );
    map4.put("ssbm","安全运营部" );
    list.add(map1);
    list.add(map2);
    list.add(map3);
    list.add(map4);

    Map<Object, List<Map<String, Object>>> map = new HashMap<Object, List<Map<String, Object>>>();
    for(int i=0;i<list.size();i++){
        Map<String, Object> personMap = list.get(i);
        if(map.containsKey(personMap.get("ssbm"))){
            List addList = map.get(personMap.get("ssbm"));
            addList.add(personMap);
            map.put(personMap.get("ssbm"),addList);
        }else {
            List<Map<String, Object>> listMaps = new ArrayList<>();
            listMaps.add(personMap);
            map.put(personMap.get("ssbm"),listMaps);
        }
    }
    System.out.println(JSON.toJSONString(map));
}


结果：
{
"行政部": [
    {
        "username": "小明",
        "ssbm": "行政部",
        "userid": "USER2015082500005"
    },
    {
        "username": "小红",
        "ssbm": "行政部",
        "userid": "USER2015082500005"
    }
],
"市场开发部": [
    {
        "username": "小懂",
        "ssbm": "市场开发部",
        "userid": "USER2015082500005"
    }
],
"安全运营部": [
    {
        "username": "小蓝",
        "ssbm": "安全运营部",
        "userid": "USER2015082500005"
    }
]

}

大概看了下，我感觉更像是一种json格式的数据转换成另外 一种json格式的数据，可以参考下json数据的操作