1-) sharedpreferences android save object class

Save List of user-defined objects to SharedPreferences
    public static final String KEY_CONNECTIONS = "KEY_CONNECTIONS";
    SharedPreferences.Editor editor = getPreferences(MODE_PRIVATE).edit();

    User entity = new User();
// ... set entity fields

    List<Connection> connections = entity.getConnections();
// convert java object to JSON format,
// and returned as JSON formatted string
    String connectionsJSONString = new Gson().toJson(connections);
    editor.putString(KEY_CONNECTIONS, connectionsJSONString);
    editor.commit();
    Get List of user-defined objects from SharedPreferences
    String connectionsJSONString = getPreferences(MODE_PRIVATE).getString(KEY_CONNECTIONS, null);
    Type type = new TypeToken < List < Connection >> () {}.getType();
    List < Connection > connections = new Gson().fromJson(connectionsJSONString, type);

DİĞER

implementation 'com.google.code.gson:gson:2.8.8'
    you can find latest version here

    Creating a shared preference:

    SharedPreferences  mPrefs = getPreferences(MODE_PRIVATE);
    To save:

    MyObject myObject = new MyObject;
//set variables of 'myObject', etc.

    Editor prefsEditor = mPrefs.edit();
    Gson gson = new Gson();
    String json = gson.toJson(myObject);
    prefsEditor.putString("MyObject", json);
    prefsEditor.commit();
    To retrieve:

    Gson gson = new Gson();
    String json = mPrefs.getString("MyObject", "");
    MyObject obj = gson.fromJson(json, MyObject.class);

kaynak : https://stackoverflow.com/questions/7145606/how-do-you-save-store-objects-in-sharedpreferences-on-android