The map replaced all the same key values ​​of the list object

I tried to replace the map data of only the selected index from the bean list, but it replaced all values ​​for every list object that contains the same key. If I create a new map object before putting the new value, then it works fine, but I wanted to know the reason why the following code is wrong.

public static void main(String[] args) {

    List<PolicyAddlnInsuredBean> lst = new ArrayList<PolicyAddlnInsuredBean>();
    PolicyAddlnInsuredBean pb = new PolicyAddlnInsuredBean();
    Map<String, Map<String, Object>> epInfoMap = new HashMap<String, Map<String,Object>>();

    Map<String,Object> map = new HashMap<String, Object>();
    map.put("addtlnInsReqd", "YES");
    map.put("selectedFlg", "No");
    epInfoMap.put("AL", map);
    pb.setEpInfoMap(epInfoMap);
    lst.add(pb);

    epInfoMap = new HashMap<String, Map<String,Object>>();
    map = new HashMap<String, Object>();
    map.put("addtlnInsReqd", "YES");
    map.put("selectedFlg", "No");
    epInfoMap.put("AL", map);
    pb.setEpInfoMap(epInfoMap);
    lst.add(pb);

    lst.get(0).getEpInfoMap().get("AL").put("selectedFlg", "Yes");
    System.out.println(lst);
}

      

        
        
        
      

    

My Pojo class:

public class PolicyAddlnInsuredBean{

  private Map<String,Map<String,Object>> epInfoMap =new HashMap<String, Map<String,Object>>(); 

  public Map<String, Map<String, Object>> getEpInfoMap() {
    return epInfoMap;
  }
  public void setEpInfoMap(Map<String, Map<String, Object>> epInfoMap) {
    this.epInfoMap = epInfoMap;
  }
  @Override
  public String toString() {
      return "PolicyAddlnInsuredBean [epInfoMap=" + epInfoMap + "]";
  }

}