How to get the data from nested Hashmap?

Question

This line of code returns List<HashMap<String, String>>

List<HashMap<String,String>> map=  restTemplate.postForObject(url,mvm,List.class);

And through this code, I can succesfully get the value of id and name in index[0].

List<HashMap<String, String>> map;
map.get(0).get("id");
map.get(0).get("name");

The Structure of the map

  HashMap<"id","1">
           <"name","john">
           <"parameters",HashMap<"key", "val"> <"key2","val2">>

How can I get data from parameters? thanks.

Answer 1

To get the value of parameter you could do

String val = ((HashMap)map.get(0).get("parameters")).get("key");

although you will need to change

HashMap<String, String> to HashMap<String, Object> for this to work

Answer 2

((HashMap)map.get(0).get("parameters")).get(map_key)

Answer 3

Try below code:

for(int i=0;i<map.size();i++){

          map.get(i).get("id");
          map.get(i).get("name");
    }

Save each value to your needed variables.

Answer 4

You can only get string values from the Map since it's declared List<HashMap<String,String>>. If it would say List<HashMap<String, Object> you could do something like this:

package com.stackoverflow.maps;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

public class InnerMaps {

    public InnerMaps(List<HashMap<String,Object>> outerList) {
        System.out.println("InnerMaps.<init>");
        for (HashMap<String, Object> outerMap: outerList) {
            for (String key: outerMap.keySet()) {
                Object value = outerMap.get(key);
                if (value.getClass().getName().equals(HashMap.class.getName())) {
                    HashMap<String,String> hashMap = (HashMap<String,String>)value;
                    System.out.println(key + ", hashMap:"  + hashMap );
                } else  {
                    System.out.println(key + " : " + value);
                }
            }
        }
    }

    public static void main(String[] args) {
        List<HashMap<String,Object>> theList = new ArrayList<>();
        HashMap<String,String> innerHashmap = new HashMap<>();
        innerHashmap.put("innerOne", "innerOneValue");
        innerHashmap.put("innerTwo", "innerTwoValue");
        HashMap<String, Object> outer = new HashMap<>();
        outer.put("one", new String("One Value"));
        outer.put("two", innerHashmap);
        theList.add(outer);
        InnerMaps app = new InnerMaps(theList);

    }
}