java - 从表中获取数据并存储在 hashmap 中

Question

我有一个包含 5 列的表格 (id |state_abbrevation | state_name | area_code | 城市)。我必须将所有值存储为键值对，其中 key= state_abbrevation 和 Value = (area_code) cities .

state_abbrevation 也有重复项。示例数据如下所示:

id | state_abbrevation |  state_name  | area_code |       cities        
----+-------------------+--------------+-----------+---------------------
  1 | AK                | Alaska       |       907 | Juneau
  2 | AL                | Alabama      |       205 | Birmingham
  3 | AL                | Alabama      |       251 | Mobile
  4 | AL                | Alabama      |       256 | Huntsville
  5 | AL                | Alabama      |       334 | Montgomery
  6 | AL                | Alabama      |       938 | Florence/Huntsville
  7 | AR                | Arkansas     |       479 | Ft. Smith
  8 | AR                | Arkansas     |       501 | Little Rock
  9 | AR                | Arkansas     |       870 | Jonesboro
 10 | AZ                | Arizona      |       480 | Scottsdale
 11 | AZ                | Arizona      |       520 | Tucson
 12 | AZ                | Arizona      |       602 | Phoenix
 13 | AZ                | Arizona      |       623 | Glendale
 14 | AZ                | Arizona      |       928 | Flagstaff
 15 | CA                | California   |       209 | Modesto
 16 | CA                | California   |       213 | Los Angeles
 17 | CA                | California   |       310 | West Hollywood
 18 | CA                | California   |       323 | Hollywood

存储在键值对中的最佳解决方案是什么，其中 key = AL & Value = 所有 state_abbrevation= AL 的区号和城市。

我想要的 HashMap 示例:核心值(value)AK，(907) 朱诺AL，(205)伯明翰 (251) 手机 (256) 亨茨维尔 [938] 938 佛罗伦萨.......等等。这是我使用 Hibernate 的工作代码:

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import org.hibernate.Criteria;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.criterion.Projections;
import org.hibernate.criterion.Restrictions;

public class HibernateCriteriaExamples {

public static void main(String[] args) {
    try {
        SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
        Session session = sessionFactory.openSession();
        Transaction tx = session.beginTransaction();

        Criteria criteria = session.createCriteria(State.class);
        //List<State> stateList = criteria.list();

        List<String> stateAbbrevationList = criteria.setProjection(Projections.distinct(Projections.property("stateAbbrevation"))).list();
        HashMap<String,List> cityAreacodeAndState = new HashMap<String,List>();

        for(int i=0; i<stateAbbrevationList.size();i++)
          {
            String abbrevation = stateAbbrevationList.get(i);
            //System.out.println(abbrevation);
            Criteria criteriaareaCodeWithCity = session.createCriteria(State.class);
            List<State> stateObject = criteriaareaCodeWithCity.add(Restrictions.eq("stateAbbrevation", abbrevation)).list();
            List<String> formattedAreaCodeAndCity =new ArrayList<String>();
            for(int j=0; j<stateObject.size();j++)
              {
                State state = (State)stateObject.get(j);
                int a = state.getAreacode();
                String b = state.getCities();
                String c = "("+a+")  "+b;
            //  System.out.println(c);
                formattedAreaCodeAndCity.add(c);
              }
            cityAreacodeAndState.put(abbrevation, formattedAreaCodeAndCity);

          }
        System.out.println("---------------PRINTING REQUIRED DATA------------------");

         for (HashMap.Entry<String,List> formattedAreaCodeAndCity1 : cityAreacodeAndState.entrySet())
          {
              System.out.println(formattedAreaCodeAndCity1.getKey() + "," + formattedAreaCodeAndCity1.getValue());
          }     

        tx.commit();
        sessionFactory.close();
    } catch (HibernateException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

}

Answer 1

您可以使用HashMap以及List。

您的 HashMap 键将为 state_abbrevation 并且您的值(即 List)将包含 area_code 和 城市。

HashMap<String, List<String>> data = new HashMap<>();
..
while(rs.next()) {
    List<String> temp = new ArrayList<>();
    temp.add(rs.getString("area_code"));
    temp.add(rs.getString("cities"));

    data.put(rs.getString("state_abbrevation"), temp);
}

获取与状态CA相关的数据

data.get("CA").get(0) //   -> gives area_code related to state "CA"
data.get("CA").get(1) //   -> gives cities related to state "CA"