Android - populate hashmap with different data types

Question

Is it possible to populate hashmap like this?

final HashMap<String, String> map = new HashMap<>();
            map.put("path", path);
            map.put("tableName", "table");
            map.put("fileType", fileType);

final HashMap<String, String> option = new HashMap<>();
            map.put("option", option.put("header", "true"));

Or is there another right (or better) way than this? because when I try to print "map" the key "option" has no value in it.

Thanks in advance

You define your `map` is a `HashMap`. But you put `option` - a `HashMap` to your `map`. That's your problem. — SonhnLab, Jul 03 '18 at 04:34
i want to put hashmap inside hashmap as a value but combine with string as a value too @SonhnLab — Rosa Gaghana, Jul 03 '18 at 04:35

score 2 · Accepted Answer · edited Jul 03 '18 at 04:42

You can't do this , you have to specify the datatype properly,

final HashMap<String, String> map = new HashMap<>();
        map.put("path", path); //path has to be a variable pointing to a string
        map.put("tableName", "table");
        map.put("fileType", fileType); // filetype has to be a variable pointing to a string

final HashMap<String, String> option = new HashMap<>(); 
        map.put("option", option.put("header", "true")); //this is wrong

HashMap<String,Map<String,String>> option = new HashMap<String,HashMap<String,String>>();
option.put("Key",map);

example: Creating and populating the maps

Map<String, Map<String, Value>> outerMap = new HashMap<String, HashMap<String, Value>>();
Map<String, Value> innerMap = new HashMap<String, Value>();    
innerMap.put("innerKey", new Value());

Storing a map

outerMap.put("key", innerMap);

Retrieving a map and its values

Map<String, Value> map = outerMap.get("key");
Value value = map.get("innerKey");

score 2 · Answer 2 · answered Jul 03 '18 at 05:40

You can store data this way:

    public static void main(String[] args){

      Map<String, String> dataMap = new HashMap<>();
      dataMap.put("key1", "Hello");
      dataMap.put("key2", "Hello2");

      Map<String, Object> map = new HashMap<>();
      map.put("1", 1);
      map.put("2", dataMap);
      map.put("3", "Value3");

      Object obj = map.get("1");
      printData(obj);

      Object obj2 = map.get("2");
      printData(obj2);

      Object obj3 = map.get("3");
      printData(obj3);

   }

    private static void printData(Object obj) {
    if (obj instanceof Integer) {
        Integer integer =convertInstanceOfObject(obj, Integer.class);
        System.out.println(integer);
    }else if( obj instanceof HashMap){

        HashMap<String, String> resMap = convertInstanceOfObject(obj, HashMap.class);

        System.out.println(resMap);
    }else if( obj instanceof String ){
        String data = convertInstanceOfObject(obj, String.class);

        System.out.println(data);
    }
}


public static <T> T convertInstanceOfObject(Object o, Class<T> clazz) {
    try {
        return clazz.cast(o);
    } catch(ClassCastException e) {
        return null;
    }
}

Output:

1
{key1=Hello, key2=Hello2}
Value3

map type is Map<String, Object> because its value can be any type of Object

score 1 · Answer 3 · answered Mar 09 '21 at 14:33

1

   HashMap<String ,Object> data= new HashMap<>();
    data.put("post",myPost);
    data.put("username",userName);
    data.put("date" ,date);

You can use different data types with HashMap in android studio-java

answered Mar 09 '21 at 14:33

talhaakkoc

81
3

Android - populate hashmap with different data types

3 Answers3