java 中List转为Map

 表结构：TmDictionary

CREATE TABLE ts_data_dic
(
  id serial NOT NULL,
  value_name character varying(30) NOT NULL, -- 值所对应的描述
  value_code character varying(20), -- 所对应的代码值
  type_code character varying(20),
  type_name character varying(30),
  comments character varying(20),
  create_by integer,
  create_date timestamp without time zone,
  last_update_by integer,
  last_update_date timestamp without time zone,
  row_version numeric(14,0) NOT NULL DEFAULT 0,
  isvalid numeric(1,0) NOT NULL DEFAULT 1,
  parent_id integer,
  editable integer NOT NULL DEFAULT 1,
  sort integer,
  CONSTRAINT pk_ts_data_dic PRIMARY KEY (id ),
  CONSTRAINT fk_ts_data_dic FOREIGN KEY (parent_id)
      REFERENCES ts_data_dic (id) MATCH SIMPLE
      ON UPDATE RESTRICT ON DELETE RESTRICT
)

实现根据传入的typeCode返回一个Map<valueCode,TmDictionary>

  public Map<String, TmDictionary> findByTypeCode(String typeCode){
    	String hql="select distinct tm from TmDictionary tm left join tm.parent parent where  tm.isValid=:isValid and tm.typeCode=:code";
    	Map<String,Object> params = new HashMap<String, Object>();
    	params.put("isValid", 1);
    	params.put("code", typeCode);
		List<TmDictionary> list=(List<TmDictionary>) dictionaryDao.query(hql, params);
        Map<String,TmDictionary> map=new HashMap<String, TmDictionary>();
        for(TmDictionary  dic:list){
        	if(dic==null){
        		continue;
        	}
        	map.put(dic.getValueCode(), dic);
        }
        return map;
    }

测试代码：

@Test
	public void findByTypeCode(){
		Map<String, TmDictionary> map= ditionaryService.findByTypeCode("lockedname");
		for(Entry<String, TmDictionary> entry:map.entrySet()){
			System.out.println(entry.getKey()+":"+entry.getValue());
		}
		
	}

原文链接：

List:

 

学号
姓名
班级
1
songjl1
01级1班
2
songjl2
02级1班
3
songjl3
03级1班
转换为Map

List<Student> list = new ArrayList<Student>();
  Map<Integer, Student> map = new HashMap<Integer, Student>();
  for(Student stu : list){
   if(stu==null){
    continue;
   }
   //Student为javabean对象.保存的数据学号,姓名,班级
   //以学号作为key.
   map.put(stu.getStuNo(), stu);
  }