How to save HashMap to Shared Preferences?

I would not recommend writing complex objects into SharedPreference. Instead I would use ObjectOutputStream to write it to the internal memory.

File file = new File(getDir("data", MODE_PRIVATE), "map");    ObjectOutputStream outputStream = new ObjectOutputStream(new FileOutputStream(file));outputStream.writeObject(map);outputStream.flush();outputStream.close();

I use Gson to convert HashMap to String and then save it to SharedPrefs

private void hashmaptest(){    //create test hashmap    HashMap<String, String> testHashMap = new HashMap<String, String>();    testHashMap.put("key1", "value1");    testHashMap.put("key2", "value2");    //convert to string using gson    Gson gson = new Gson();    String hashMapString = gson.toJson(testHashMap);    //save in shared prefs    SharedPreferences prefs = getSharedPreferences("test", MODE_PRIVATE);    prefs.edit().putString("hashString", hashMapString).apply();    //get from shared prefs    String storedHashMapString = prefs.getString("hashString", "oopsDintWork");    java.lang.reflect.Type type = new TypeToken<HashMap<String, String>>(){}.getType();    HashMap<String, String> testHashMap2 = gson.fromJson(storedHashMapString, type);    //use values    String toastString = testHashMap2.get("key1") + " | " + testHashMap2.get("key2");    Toast.makeText(this, toastString, Toast.LENGTH_LONG).show();}

private void saveMap(Map<String,Boolean> inputMap) {    SharedPreferences pSharedPref = getApplicationContext().getSharedPreferences("MyVariables", Context.MODE_PRIVATE);    if (pSharedPref != null){        JSONObject jsonObject = new JSONObject(inputMap);        String jsonString = jsonObject.toString();        pSharedPref.edit()            .remove("My_map")            .putString("My_map", jsonString)            .apply();    }}private Map<String,Boolean> loadMap() {    Map<String,Boolean> outputMap = new HashMap<>();    SharedPreferences pSharedPref = getApplicationContext().getSharedPreferences("MyVariables", Context.MODE_PRIVATE);    try {        if (pSharedPref != null) {            String jsonString = pSharedPref.getString("My_map", (new JSONObject()).toString());            if (jsonString != null) {                JSONObject jsonObject = new JSONObject(jsonString);                Iterator<String> keysItr = jsonObject.keys();                while (keysItr.hasNext()) {                    String key = keysItr.next();                    Boolean value = jsonObject.getBoolean(key);                     outputMap.put(key, value);                }            }        }    } catch (JSONException e){        e.printStackTrace();    }    return outputMap;}